Physicalism and the
Bogey of Determinism
Aaron Sloman
School of Computer Science
The University of Birmingham
(Written when I was at the University of Sussex).
Presented at an interdisciplinary conference on Philosophy of Psychology at the University of Kent in 1971. Published in the proceedings, as
A. Sloman, 'Physicalism and the Bogey of Determinism'
(along with Reply by G. Mandler and W. Kessen, and additional comments by Alan R. White, Philippa Foot and others, and replies to criticisms)
in Philosophy of Psychology, Ed S.C.Brown, London: Macmillan, 1974, pages 293--304. (Published by Barnes & Noble in USA.)
Commentary and discussion followed on pages 305--348.
This paper rehearses some relatively old arguments about how any coherent notion of free will is not only compatible with but depends on determinism. However the mind-brain identity theory is attacked on the grounds that what makes a physical event an intended action A is that the agent interprets the physical phenomena as doing A. I should have added "... and controls the details".

The paper should have referred to the monograph Intention (1957) by Elizabeth Anscombe (summarised here by Jeff Speaks), which discusses in detail the fact that the same physical event can have multiple (true) descriptions, using different ontologies.

My point is partly analogous to Dennett's appeal to the 'intentional stance', though that involves an external observer attributing rationality along with beliefs and desires to the agent. I am adopting the design stance not the intentional stance, for I do not assume rationality in agents with semantic competence (e.g. insects), and I begin an attempt to explain how an agent has to be designed in order to perform intentional actions; the design must allow the agent to interpret physical events (including events in its brain) in a way that is not just perceiving their physical properties.
Some of the ideas in the paper and in my responses to commentators (below) were later presented in The Computer Revolution in Philosophy (1978), including a version of this diagram (originally pages 344-345, in the discussion section below), discussed in more detail in Chapter 6 of the book, and later elaborated as an architectural theory assuming concurrent reactive, deliberative and metamanagement processes, e.g. as explained in this 1999 paper Architecture-Based Conceptions of Mind, and later papers, and crudely depicted here.
A PDF version is available as
(Last updated: 2 Aug 2018)

Physicalism and the
Bogey of Determinism
Only a dreadful prig could seriously condemn secret lust as a
form of adultery. However, even someone who claims to be
wholly concerned with the things of the mind must have
some interest in what he says and does, and these require the
occurrence of bodily processes. Realising that so much of
what matters to us involves physical events and processes, it
is natural to find alarming the suggestion that all physical
behaviour of our bodies can be explained in terms of the
'mindless' workings of laws of nature. Consequently, many
philosophers have tried to prove it isn't so.
More precisely, the attempt to refute physicalism (the
theory that human bodies are physical systems) may be
motivated by the assumption that it implies all the following:
that all our actions are predictable; that mental phenomena
are identical with or composed of physical phenomena; that
all human actions have purely physical explanations; and that
there is no room for beliefs, desires and other mental
phenomena to influence our actions. I shall argue first of
all that since the question whether human bodies are physical
systems is an empirical one, attempts at philosophical
refutation are futile, and secondly that physicalism does not
have the implications just mentioned. This will require a

1I am indebted to several colleagues, including M. Boden, D. Booth, J. W. Burgess,
M. B. Clowes, J. Dorling, M. Ireland, R. Poole, T. L. Sprigge, A. R. White, for
comments on an earlier version of this paper, and to N. S. Sutherland, many of
whose arguments I have borrowed from his 'Is the brain a physical system?', in R.
Borger and F. Cioffi (Eds.), Explanation in the Behavioural Sciences (Cambridge
University Press, 1970) pp. 97-122.

284 space Determinism
lengthy discussion of the relation between actions and
movements, or between mind and body.
First, let us be clear which thesis is under discussion.
To avoid semantic problems arising out of the future growth
of physics, let us agree now to use the word 'physics' to cover
what is called physics in present day physics departments in
respectable universities. This embraces a set of empirical and
theoretical concepts, including a set of scales of measurement,
a body of theory and a host of experimental and
mathematical techniques. The existence of borderline cases
arising out of current disputes at the research frontiers makes
no difference to our present concerns. (I have not included
control engineering as part of physics, though it is relevant to
much of the discussion, since its concepts are intermediate
between physical and psychological concepts.)
Whatever may be unclear about what falls within physics
thus defined, it is indisputable that physics does not include
such concepts as 'smile', 'want', 'jealous', 'reply', and that the
theories of physics do not include such statements as 'If a
person prefers X to Y, but knowingly chooses Y rather than
X, then he must have some other preference, hope, fear,
dislike or attitude to which X and Y are relevant'. It is
equally clear that human bodies contain physical substances,
that they have many physical properties, that many physical
processes occur in them, and that physical movements and
other physical processes are involved whenever we say or do
Using the term 'physical behaviour' to describe any
movement, process or change of state completely characterisable
by means of concepts of physics, we can sum up by
saying that it is an obvious empirical fact that many of our
actions in some sense involve physical behaviour. One of the
problems to be discussed below is what sort of involvement
this is.
Another problem is whether the following 'Physicalist'
thesis is true, and what its implications are:

Physicalism and the Bogey of Determinism space 285
(P) All the physical behaviour (in the sense just defined) of
human bodies or parts thereof conforms to current
physical theories.
By 'conforming to' current physical theories, I mean not
merely failing to refute such theories, but also being
predictable and explainable on the basis of such theories,
except in so far as the theories themselves require certain
physical happenings (e.g. some subatomic events) to be
unexplainable. Since current physics is compatible with the
existence of a mechanism in which there is significant coupling
between random subatomic processes and large scale bodily
movements (e.g. a robot whose changes of speed and
direction of motion are partially controlled by switches
triggered off by radiation from a lump of uranium inside it),
thesis (P) does not imply that all the physical behaviour of
human bodies is predictable on the basis of current physical
theory and suitable measurements made in advance. However,
it is clear that not much of our behaviour is significantly
coupled with random processes, since if it were humans
would be much less reliable and predictable than they are.
(P) is obviously a special case of the more general thesis:
(P1) All physical behaviour, (i.e. of human bodies and
everything else) conforms to current physical theories.
Both (P) and (P1) are empirical. Whether the physical
behaviour of some object conforms to current physics is
clearly an empirical question, even though it may be very
difficult to discover the answer. It is relatively easy to
establish beyond all reasonable doubt by examination of its
mechanism, that the physical behaviour of a clock conforms
to current theories, even though there is always the possibility
that more refined measurement or observation may
show that the examination missed something such as an
incongruous relation between the molecular structure of the
spring and its tension. It is not easy to establish beyond all
reasonable doubt that the behaviour of some system does not
conform to current physics, least of all when the system is as
complex as the human brain. Still, it is conceivable that the

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behaviour of a relatively simple part of the brain may one
day be shown, beyond all reasonable doubt, to refute some
generalisation of modern physics, especially if the behaviour
is then adequately explained by some quite new theory. I
have gone into some obvious details here because it seems
that some philosophers who argue against determinism fail to
realise that if successful, their arguments would refute an
empirical theory.
(P1 ) is a version of the thesis of universal determinism,
perhaps the only sort of version worth taking seriously in
view of the indeterministic implications of modern physics.
(P) is a more modest version of the same thesis, restricted to
the human body. Philosophers have occasionally tried to
show that determinism is incoherent or internally inconsistent,
but such attempts are futile as far as (P) and (P1) are
concerned, since they are empirical and therefore not
amenable to philosophical refutation. This does not rule out
the possibility of an empirical refutation based on common-sense
knowledge about what humans can do, but this is not
as simple a matter as might be thought since (a) it would
require a much clearer grasp of the totality of possible
physical mechanisms than anybody has at present (e.g. it is
not at all obvious that every physical information-processing
mechanism must be a Turing machine), and (b) it would
require an account of the relation between common-sense
concepts used in the description and explanation of human
behaviour and the concepts and measurement scales of
physics. It is worth dwelling on (b) in order to get a clearer
understanding of what (P) does and does not imply.
Normal perception and thought about our own behaviour
and the behaviour of others use concepts and categories
which are not part of physics. When we say (or think) such
things as 'W has at last made up his mind which job to
accept', 'X beat up his wife in a fit of temper', 'Y walked
hurriedly towards the door', 'Z found a way of refuting
Fermat's last theorem yesterday', our descriptions and
explanations use concepts which presuppose that we are
referring to conscious agents with beliefs and intentions
concerning the actions they perform. Since common-sense
knowledge about human behaviour uses such concepts, and

Physicalism and the Bogey of Determinism space 287
since (P) does not explicitly say anything about human
actions or mental phenomena, there is no direct conflict
between (P) and common sense. However, our problem is
whether indirect conflict is possible, and if so how. The
answer must depend on the relation between human actions
or mental processes and the underlying physical behaviour.
What is this relation? It is by now a commonplace that action
descriptions and physical descriptions operate at different
'levels'. (See Waismann's article on 'Language strata' in Logic
and Language,
Vol. 2, ed. A. G. N. Flew.) But exactly what
this distinction of levels amounts to, and what the relationship
is between the different levels remains to be made clear. Unfortunately
the relationship is very complex: there is not just
one difference between the level of physical description and
the common-sense level, but several. For instance, one
difference is that the use of certain common-sense descriptions
and explanations expresses moral or other values of the
speaker ('As soon as the alarm sounded he made a very
cowardly dash for the exit'), or may express a preparedness in
principle to treat the subject of the descriptions in a certain
sort of way, such as a preparedness to feel pity should the
subject suffer, or a willingness to praise or blame the subject
for what he has done. Such connotations about the speaker's
values or attitudes are missing from descriptions in the
terminology of physics. But the particular relation between
the level of physics and the level of actions and mental
phenomena that I want to discuss is that of interpretation.
It is tempting to suppose that when the performance of an
action involves certain physical behaviour (e.g. certain movements,
or the production of a pattern of acoustic radiation
from the mouth) the action is somehow composed of the
physical behaviour, or constituted by it. A stronger claim is
that the two are identical. That both claims are false follows
from the fact that the physical behaviour has to be
interpreted (by the agent and by others) as the action, and
different interpretations are possible, depending on the
immediate social or psychological context. This is most

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obvious in the case of speech, for the utterance of the same
sequence of sounds may, on different occasions, be interpreted
as the making of quite different statements. But even
the physical behaviour involved in my action of walking to
the door may on another occasion be involved not in walking
to the door but in doing the exercises recommended by a
physiotherapist. A movement of the hand may in one culture
be interpreted as a friendly gesture, in another as threatening.
Thus, what action is performed when a certain physical
behaviour occurs is relative to a mode of interpretation.
When I observe and describe someone's action I normally
interpret the physical configuration which I perceive, in the
light of an enormous amount of knowledge which I normally
use automatically. I may use knowledge of the normal mode
of interpretation of that kind of behaviour in my society. I
may use knowledge of the mode of interpretation most likely
to be employed by that particular agent (i.e., what he intends
himself to be doing, and also how he interprets what he
observes his body to be doing: these can, but don't normally,
come apart), and this may be based on a deep personal
knowledge of the agent, or merely on some arbitrary
agreement we have entered into, or on what he has been
doing or saying in some short preceding interval. I may use
knowledge of the normal, and generally recognised, function
or purpose
of some object or equipment he is manipulating,
such as a pencil, or light-switch, and interpret him as using it
for its normal purpose. Some aspects of my interpretation of
the physical input or my sense-organs may be largely (though
usually not entirely) determined by my genetic make-up,
such as the automatic peripheral processing done by the
optical system which gives me information about colours,
edges, textures, movements, orientations, etc., of the objects
I see, or the decomposition of complex sound waves into
distinct sounds each with its own pitch and timbre. The
normal adult human being has enormous interpretative
resources: his visual apparatus can quickly find a suitable
syntax (or 'grammar') for analysing the structure of a wide
variety of visual configurations, and interpretative rules for
interpreting such structures as objects standing in certain
relations, with functions of certain sorts, or as persons

Physicalism and the Bogey of Determinism space 289
consciously performing certain actions, or as a social situation
involving several persons with complex interactions
between them (e.g. observing a group in the middle of a
heated argument). That we find this so natural, that we do it
all effortlessly, and that we normally all agree in our
interpretations, obscures the fact that interpretation is
involved. (For similar comments on the perception of
pictures see E. H. Gombrich Art and Illusion, and N.
Goodman Languages of Art. Max Clowes helped me to
understand the importance of interpretation.)
But if being composed of (like being identical with) is a
two-termed relation, then it cannot be the relation between
physical behaviour and the action it expresses (or represents),
for the latter relation is relative to a mode of interpretation,
M, which can vary. Thus there is a three-termed relation
between the physical phenomenon X, the action (or psychological
phenomenon) Y, and M. Which mode of interpretation
is the correct one will, as I have indicated, depend on
different factors on different occasions. Sometimes there are
different ways of interpreting the behaviour, none more
correct than the others, in which case the behaviour is
ambiguous, perhaps intentionally so. Sometimes no interpretation
can be found: it is a 'meaningless' twitch or spasm, or
whatever. People who find it unusually difficult to interpret
the behaviour of others, or whose behaviour most normal
people cannot interpret, may be regarded as mentally ill.
(This issue is complicated by the fact that there are so often
several layers of interpretation.) That what a physical or
geometrical configuration expresses or represents is relative
to a mode of interpretation is part of the explanation of the
fact that there are no geometrical theorems to the effect
that certain configurations of lines represent (or look like)
faces, and also the fact that it is not possible to give necessary
and sufficient conditions in purely physical and geometrical
terms for something's being a picture of a smiling face, or for
something's actually being an act of smiling at another
Since the relation between action descriptions and descriptions
of physical behaviour involves a third term which can
vary, there are very few direct implications between the two

290 space Determinism
levels of description. This is again particularly clear in the
case of linguistic actions: 'He asked me the time' reports an
action unambiguously, but leaves quite unspecified what the
physical vehicle was: whether a spoken sentence was uttered,
and if so in which language, and if not whether the request
was written down, or perhaps made in some sign-language,
etc. Even when the relevant mode of interpretation and the
form of physical behaviour are partly specified, as in 'He
asked me, out loud, in English, what the time was', the
possible range of physical configurations compatible with the
action description remains very large, as may be seen by
comparing harmonic analyses of tape recordings of different
people saying 'What is the time?'
Now one of the things which is not part of common-sense
knowledge, at least not explicitly, is exactly what the various
modes of interpretation are which we use so frequently. The
difficulty of making them explicit is illustrated by the
difficulty of formulating a theory of the semantics of a
natural language: this is difficult even for native speakers. But
without explicit formulations of our interpretative resources,
which would probably require the combined efforts of
psychologists, linguists, art historians, computer scientists
and philosophers, it is not possible to spell out in detail the
physical implications of common-sense knowledge and beliefs
about what humans can do. Thus, any empirical refutation of
thesis (P) on the basis of the indirect implications of common-sense
seems to be out of the question at present.
The desire to refute one or other form of determinism seems
to be very strong in many people: this is the only way in
which I can account for the proliferation of very bad
arguments against it which I have read and heard in
philosophical discussions. Apart from irrational and emotional
factors which may explain such a desire, I believe there
are also some straightforward mistakes as to what is implied
by a thesis such as (P). For instance, it may be mistakenly
thought that (P) implies that there are no such things as
mental states or processes, or that all our actions can be
explained (at least in principle) purely on the basis of current

Physicalism and the Bogey of Determinism space 291
physical theory, or that even if there are mental phenomena they can have no influence on our actions.
However, a careful reading will show that neither (P) nor (P1) says anything about the existence or non-existence of non-physical things, or mental phenomena in particular. At most (P) and (P1) imply that all physical events and processes can be explained without reference to any such things. (Not even within the margins of quantum indeterminacy can 'non-physical' causes influence physical events, since that would interfere with physically predictable probability distributions.) Thus (P) is compatible with epiphenomenalism.
Does (P) imply that there are physical explanations of all our actions? If my action A involves physical behaviour B, and there is a complete physical explanation of B, does this not thereby explain the occurrence of A? No, for suppose S1 is a statement describing B (and therefore using only concepts of current physics) and S2 a statement describing the action A. Then in agreeing that this occurrence of B is to be interpreted as the performance of A, we are using some mode of interpretation, call it M. Suppose E1 is the statement explaining, in terms of current physics, the behaviour described in S1. Now, I think that without committing ourselves to any detailed analysis of the concept of explanation we can say that there must be some relation between E1 and S1 in virtue of which the former provides an explanation of the behaviour. For instance, it may be that E1 logically entails S1 or logically entails that what S1 says is probably true. But because S1 does not entail S2, or stand in any two-termed relation analogous to entailment (recall that A is not composed of B), the only way to get an explanation of the action out of E1 is to conjoin with it a statement to the effect that B is to be interpreted according to M, for according to a different mode of interpretation S1 may be true and S2 false. It may be that this enlarged statement stands in the required relation to S2 . But then even if it does give an explanation of the action, it will not be a purely physical explanation for such statements about modes of interpretation are clearly not parts of physics. Thus (P) does not entail that there is a purely physical explanation of every human action.

292 space Determinism
It might be thought that (P) entails that there cannot be
psychological explanations of our actions, for instance in
terms of the agent's desires and beliefs, because if there were
such an explanation of an action it would also explain the
physical behaviour involved in the performance of that
action, thus invalidating the supposed physical explanation.
But if E2 is such an explanation of the action described in
S2 , the same argument as before shows that on account of
the elasticity of the relation between S2 and S1, E2 need not
provide an explanation of the behaviour described in S1, even
though S2 gives an interpretation of that behaviour. Indeed,
one can know what action a person performed, and can have
a perfectly adequate psychological explanation of it, without
having any idea what sort of physical behaviour was involved,
as the example of asking the time shows. This is like knowing
a computer's solution to a problem, and being able to explain
its solving the problem by specifying the methods the
computer uses, without being able to describe or explain the
physical output of the computer (e.g. a complex wave-form
on magnetic tape). One may not even know whether the
computer uses valves, transistors, or components of a quite
different kind. But there must be some underlying physical
behaviour with its own explanation. (This point is discussed
more fully in Margaret Boden's Purposive Explanation in
(Harvard University Press, 1972).)
A similar problem can be raised in terms of the concept of
'cause' or 'influence', instead of 'explanation'. It might be
thought that (P) implies that such things as beliefs and desires
cannot influence our actions, since it implies that the
physical behaviour of our bodies is fully determined by
physical antecedents and processes, leaving no room for
psychological phenomena to make any difference. If beliefs
and desires can influence our actions, then since actions
involve physical behaviour of our bodies, it follows that
beliefs and desires can influence physical behaviour of our
bodies. How can non-physical things like beliefs and desires
influence physical events and processes if the latter are
completely determined physically? It seems that either (P) is
false or mental phenomena do not influence our actions, or
else influencing actions is possible without influencing the

Physicalism and the Bogey of Determinism space 293
underlying physical behaviour. The concepts of 'cause' and
'influence' are treacherous and it is worth reflecting on this
last suggestion that the relation between our actions and the
physical behaviour of our bodies does not include any causal
It would be possible to argue that there are no causal
connections between physical phenomena and either actions
or mental phenomena, if, as has often been supposed since
Hume, the existence of a causal connection were nothing
more than the existence of a predictively reliable inductive
correlation between two general types of events, or properties
or states of affairs. For if the relation between physical
phenomena and actions or mental phenomena is not a
two-termed one, but involves also a third term, a mode of
interpretation, then since different modes of interpretation
may be appropriate in different circumstances, there need be
no reliable inductive correlations between physical phenomena
and actions or mental phenomena. Thus, it does not
follow from (P) that empirical investigation could yield such
correlations, or that instruments recording physical processes
in our brains can be used, on the basis of such correlations, to
give information about the contents of our minds.
There are indeed many good correlations between physical
and mental phenomena, but these concern only general
feelings or moods, or general aspects of cognitive functioning.
It may be possible to tell from the physical or chemical
processes in a person's body that he feels fear, or anxiety, or
depression, but it is unlikely that generally applicable
procedures could reveal that he fears that an attempt will be
made to blow up the aeroplane in which he is travelling, or
that he is anxious about his prospects as a candidate in the
next election, or that he is depressed about his daughter's
failure to win the local beauty competition. Electronic
instruments may be able to register whether I am conscious
or not, but not that I am conscious that the ticking of the
clock in the hall is slower and less regular than usual. If a
particular part of the brain is solely concerned with decision-making,
there may be a neuro-physiological indication that I
am taking a decision, but not that I am deciding whether to
drive to London by car, despite the greater expense, or to go

294 space Determinism
by train, despite the greater inconvenience. For it is likely
that the languages, or codes, used by human brains vary not
only from culture to culture (think of the occurrence of the
above moods, feelings, thoughts, etc. in an Englishman, a
Frenchman and a Chinaman), but also from one individual to
another, since the sense which I associate with a proper name
or other referring expression, and to a lesser extent with
descriptive expressions too, depends to a considerable extent
on exactly what I know about the thing (or things) referred
to, that is, it will depend on my previous learning theory. (I
have argued this more fully elsewhere.) This linguistic
variation is limited by social constraints as far as our written
and spoken language are concerned, for we could not
otherwise communicate with one another. But there are no
such constraints on the modes of representation used by our
brains for the storage and processing of the enormous
amount of information each of us has to handle: so
tremendous individual variation is possible.
The point is simply that what makes some particular
physical configuration or process in my brain (or physical
output of my body) have the function it does, or express or
represent what it does, depends on a complex set of
interrelationships with other things in the brain and their
relationships (via sense organs and various kinds of motor
output systems) to a complex set of present and past
phenomena, including cultural phenomena, outside my body.
An extreme case should make this clear. When a Chinaman
and I both hear a spoken Chinese sentence there may be a
very similar pattern of electrical activity produced thereby in
certain parts of our brains. But I can interpret the sound only
as somebody talking, whereas the Chinaman will perhaps hear
a detailed report of a horrifying disaster in which his children
have died.
This shows that (P) is perfectly consistent with the view
that it is a complete waste of time looking for general (i.e.
interpersonal) inductive correlations between mental contents
and brain phenomena. Neither does acceptance of (P)
commit one to taking seriously the prospect of fiendish
neuro-physiologists using instruments to read the contents of
our thoughts, beliefs, intentions, etc., by direct physical
manipulation of our brains. Of course, if the physical

Physicalism and the Bogey of Determinism space 295
behaviour of our brains conforms completely to current
physical theories, then that does imply that it is possible for a
physical system to interpret physical phenomena in terms of
psychological categories, for that, in effect, is what a brain
does. But the preceding discussion shows that (P) is perfectly
compatible with different brains doing things in different
ways. So the problem of designing an instrument which will
read my mind off my brain may be no less than the problem
of designing a replica of my brain (or parts of it). The output
of such an instrument will then be related to the contents of
my brain in much the same way as my verbal output is
related to the contents of my brain.
Despite the interest and importance of this point that
physical phenomena are related to actions and mental
phenomena via variable modes of interpretation, and therefore
need not be significantly correlated with one another, it
does not prove that there are no causal connections between
the two levels, for the argument rests on an analysis of the
concept of 'cause' which is at least controversial. In any case,
it is an indisputable fact that by giving information I can
change someone's beliefs, which can cause a change in his
desires and intentions and thereby influence his actions and
the physical movements of his body. Similarly, the physical
process consisting of the arrival at his ear-drums of a certain
pattern of acoustic radiation can cause a change in his beliefs,
desires, intentions and actions.
For, in such cases, the mode of interpretation is fixed.
Given that the physical phenomena are interpreted according
to mode M, then certain changes at the physical level are
necessary for changes at the level of actions, intentions, etc.,
and conversely certain changes at the latter level necessarily
involve certain changes at physical level. Admittedly, since M
can vary, these changes at different levels are not in
necessary and sufficient conditions for one
another. But in a situation where the mode of interpretation
is fixed (e.g. by social conventions and the brain structure of
the persons concerned), occurrences at one level can be
necessary, or sufficient for occurrences at the other.
So, despite the logical independence of events and processes
at the two levels, and despite the lack of any general
inductive correlation between them, nevertheless in a context

296 space Determinism
in which the mode of interpretation linking the two levels
remains fixed the two levels are inextricably intertwined, and
processes at one level are only possible if certain processes
occur at the other level. So, when it is argued that if (P) is
true, then our physical behaviour, and therefore also our
actions, are fully determined by antecedent physical events
and processes, leaving no room for such things as beliefs and
desires to influence our actions, the mistake is to apply the
mode of interpretation which links our physical behaviour
with our actions, while forgetting that the antecedent
physical events and processes in the brain are also to be
interpreted in terms of psychological concepts. To argue that
the beliefs, desires, etc. have no influence because changing
the physical causes must change the actions, and changing the
beliefs, desires, etc. will not influence the actions so long as
the physical antecedents are not changed, is to forget that so
long as the relevant modes of interpretation remain fixed
the physical antecedents cannot be different unless the
psychological antecedents are, and the psychological antecedents
cannot be different unless the physical ones are.
Of course, it is possible to interfere with the physical
workings of my brain in such a way that the original
interpretative system is no longer operative, for instance by
destroying part of my brain or giving it excessive electrical
stimulation: but then the resulting physical behaviour of the
body is no longer interpretable at the level of actions. It may,
for instance, be something like an epileptic fit. That physical
occurrences can totally disrupt mental life and the performance
of actions, is thus not a new paradoxical consequence of
(P), but a familiar fact which any theory of the mind—body
relation must accommodate.
I am painfully aware that I have barely begun the difficult
task of describing the complex and confusing relation
between the different levels of description and explanation.
We seem to need new organising concepts here to bring out
clearly the difference between the case where two logically
independent processes can interact because one is an interpretation
of the other, and the case of two separate processes at

Physicalism and the Bogey of Determinism space 297
the same level causally interacting because they are linked by
wires, levers, radiation, etc. The latter case is a misleading
analogy which keeps intruding and generates apparent paradoxes.
In a mechanism like a computer or a brain, there is a
kind of organisation which ensures that, so long as the system
is working normally, the physical structure constrains the
physical processes that can occur, in such a way that they are
all, so to speak, 'harnessed in the service of processes at a
different level. But the relation is not like that between an
engine and the pump or other machine which it drives, but
like that between the configuration of charcoal on the
surface of a sheet of paper and the picture of a smiling face,
which we take it to be. The relation is at once remote, since
it is mediated by a mode of interpretation, and intimate,
since, given the mode of interpretation, the existence of
either the physical object or the picture is necessary and
sufficient for the existence of the other. It is this intimacy
which has misled some philosophers into thinking the
philosophically important relation between the two levels is
one of identity, or composition.
I have tried to show that the attempt to draw alarming or
paradoxical conclusions from the thesis (P) may rest on a
failure to grasp the complexity of the relation between
physical states and processes on the one hand and our
actions, beliefs, desires, decisions, etc., on the other. No
doubt I have generated more problems that I have solved, for
I have said little about the contents of the modes of
interpretation, nor explained in detail how to tell which
mode of interpretation is correct in any particular case.
Neither have I shown what sort of organisation of a physical
system can constrain its behaviour in such a way as to make
it interpretable in terms of psychological concepts. These are
matters for further inquiry. But the existence of computers
which everybody agrees to conform to thesis (P) even though
they can calculate, solve problems, search for significant
correlations in a mass of data, control complex machines,
etc., shows that concepts operating at different levels can get
a grip on the same bit of the world.

298 space Determinism
As a step towards showing how psychological concepts can
get a grip on a system whose physical behaviour conforms to
physical theory, I shall now attempt to list a set of conditions
whose conjunction seems to be a sufficient condition for the
applicability of concepts like 'believe', 'want', 'decide',
'intend', and verbs of action, as we normally understand
them. There are immense difficulties in practice in designing
a physical system which satisfies these conditions (despite the
optimism of the edition of Science Journal entitled 'Machines
Like Men', Vol. 4, No. 10, October 1968), but there does not
seem to be any logical or conceptual impossibility. Each
condition presupposes the satisfaction of some or all of the
preceding conditions, and adds a new type of sophistication.
My formulations here are sketchy: greater precision would
require too much space. The conditions follow.
1.   The system is an integrated whole whose parts are
controlled by or provide input to a central processing
machine. It contains sensors capable of receiving stimuli of
various sorts from the environment and motors (e.g. limbs
and muscles capable of changing the environment, changing
its relation to the environment (e.g. position and orientation)
and possibly changing the positions and orientations of its
own parts relative to each other.
2.   Its input processors are capable of analysing and
recognising at least some of the sensory patterns, including
temporal patterns, that humans can perceive, such as two-
and three-dimensional shapes and their movements, and
perhaps certain sound patterns. The processing is normally
quick enough for configurations to be recognised before they
3.   It can organise at least some of its output into patterns
that humans can recognise and describe such as picking
something up, moving three yards, and putting it down,
drawing simple polygons, or producing recognisable sound-patterns.
These types of output are among the configurations
its input processors can recognise.
4.   The central mechanism can use the input from the
sensors, possibly together with feedback from its output, as a

Physicalism and the Bogey of Determinism space 299
basis for constructing an internal model or representation of
some aspects of the environment and its own relations to the
contents of the environment (e.g. its position and direction
of motion).
5.   It is capable of using this representation as a basis for
moving around the environment and as a basis for constructing
hypothetical, or provisional, representations of previously
unknown aspects of the environment, these representations
then being modified, discarded, retained as provisional, or
built into the main representation of the environment,
depending on new input.
6.   It has a set of long-term goals (including the goal of
constructing as complete and accurate a representation of the
environment as possible, and maintaining itself in good
working order), and a set of transient goals, and some or all
of its behaviour is directed to the attainment of these goals.
The goals are to some extent ordered as to priority, and there
is a mechanism for imposing further ordering or generating
new goals (either randomly, or in relation to higher-order
goals) when conflicts arise between two or more goals.
7.   It is capable of using its representation of the environment
as a basis for working out possible or efficient means to
the achievement of its goals (e.g. working out a route to get
to a place or type of object required by one of its goals), in
which case it adds the adoption of those means to its store of
goals (subject to the above condition about conflicts).
8.   It can construct a representation of some aspects of its
own internal states and processes, including such things as
what its goals are, what the form and contents of its
representation of the environment are, what procedures it
uses to select means or resolve conflicts between its goals,
etc. It can change its internal state when this is a means to
the achievement of one of its goals.
Of any system satisfying all these conditions it seems to
me that it would be perfectly in order to use the following
descriptions as I understand them: 'There are some things it
knows, and some things it believes, though mistakenly.'
'There are some things it wants to have or do, and others it
wants to avoid.' 'It prefers some things to others.' 'It does
this with the intention of doing that.' 'At first it did not

300 space Determinism
intend to do this, but after deliberating about the alternatives
it changed its mind.' 'There are some things it is aware of,
others it is not aware of (e.g. in its environment) at any time.'
Further, explanations of its actions could be given in terms of
beliefs and desires, for instance, 'It pushed the chair from the
doorway because it wanted to replace its batteries and
believed that a stock of fresh batteries was in a box in the
next room, and that it could only get to the next room by
moving the chair then going through the door.' However, the
physical events and processes involved in all this might be too
complex for an explanation of the physical behaviour in
terms of current physical theory to be a practical possibility,
even though it was known from the initial design and
construction that the system conformed to thesis (P1), i.e. it
was a physical system.
New levels of sophistication in the types of action it can
perform, and in the kinds of mental phenomena which can be
ascribed to it would arise out of the satisfaction by the
system of a further condition:
9. It can use a language to communicate with us or with
others like itself about the contents of the environment, its
own internal states and processes, its goals, its unsolved
problems, etc. That is, it can translate from an internal
representation into an external language and vice versa, and
can use linguistic devices to indicate whether it is requesting
information, reporting something it accepts as correct,
formulating a hypothesis for discussion, etc., i.e. illocutionary-act
If this additional condition were satisfied, we could talk
about telling it things, persuading or advising it, bargaining
with it (e.g. 'If you will carry this box across the road for me,
I'll re-solder your faulty connections') etc. We could influence
its behaviour in these ways, that is by influencing its beliefs
or desires, even though the underlying physical processes
were too complex for us to comprehend. It would clearly
no longer be true to say of such a system that all it does is
what its designer intended it to do. Several such systems
interacting with one another could form a community
engaged in various co-operative enterprises and develop
various conventions for dealing with possible or actual

Physicalism and the Bogey of Determinism space 301
conflicts (e.g. law courts) or for making conflicts less likely
(e.g. traffic regulations), etc. Confronted with an autonomous
community of such robots, we should surely find it
intolerable to sustain the clumsy circumlocutions some
people would at first want to use in describing and explaining
their behaviour because they know 'those things are only
physical mechanisms'. There seems to me to be no conceptual
mistake involved in thinking that it would be morally
wrong not to regard such things as conscious, intelligent,
responsible for their actions and worthy of being treated with
consideration for their desires and interests.
Of course, I cannot yet rigorously prove that a physical
system could satisfy the conditions (1)—(9), or even conditions
(1)—(8): that would require me to design a system satisfying
these requirements, or else to prove that the human (or some
animal) brain is a physical system. I doubt if anyone can yet
design such a system, though the development of computer
science holds out encouraging prospects. (The formulation of
some of the conditions was influenced by a paper by Max
Clowes, 'On seeing things' in Artificial Intelligence Vol. 2,
1971, describing a computer programme for the interpretation
of pictures of polyhedra.)
Anyone who wished to argue against the position in this
paper must argue that a physical system could not satisfy the
conditions listed, or that the conditions are not sufficient to
justify the ascription of psychological predicates and explanations.
To establish the latter would involve specifying some
necessary condition which is not entailed by the conjunction
of my conditions.
Unfortunately, the issue is in part bedevilled by the
indeterminacy of our concepts. For instance, if anyone
claims that an additional condition is being a member of
some biological species which has evolved naturally, which
would rule out artefacts, then I cannot argue against this
except to say (a) that my own concepts have no such
limitations and (b) that situations could arise in which
insisting on this condition as necessary would lead to easily
avoidable terminological complexity. I could also try to show
that the restriction would be immoral, but a contrary moral
position, that artefacts ought not to be treated as conscious

302 space Determinism
being with beliefs, etc., can be consistently maintained, as
can a similar moral attitude to dogs, cats, slaves, or members
of the 'lower' classes. However, apart from the moral
implications, a disagreement on whether the biological
condition is necessary for the applicability of psychological
concepts seems to have no philosophical interest: it seems to
be a purely terminological disagreement. Further, the intelligibility,
to many readers, of science fiction stories in which
such concepts are applied to robots of various sorts seems to
me to show that I am in large company in not finding the
biological condition logically or conceptually necessary.
My list of conditions does not explicitly include the
possession of 'inner experience', the sort of content of
consciousness that we are 'directly aware of, etc. This, it
could be argued, shows that the conditions are not sufficient to
justify talk of mental phenomena. Part of the reply to this
objection is that the claim that robots satisfying all my
conditions also have this inner world would be no more (and
no less) problematic than the claim that other human beings
do. No doubt some such robots of the future will be
convinced that they are not mere physical systems since they
do have this 'something extra' which they can identify for
themselves by focusing attention inwards. There is no
conceptual difficulty in supposing that such a robot might
learn that its sensory systems can mislead it, and that it can be
given hallucinations by a malevolent human being: and this
might lead it along the well-worn track to the conclusion that
the only thing it can be sure of is the content of its own
consciousness, since even the supposed existence of its body
and an external world could be merely a complex illusion.
But there are further subtleties underlying the appeal to
this extra condition. We are able intelligibly to talk about our
private inner experience, the contents of our sensations, etc.,
as inaccessible to other people because of the following facts.
Whatever I can refer to it is possible for someone else to refer
to also. However, the manner in which I am able to identify
it (its 'mode of presentation' to me, in Frege's terminology)

Physicalism and the Bogey of Determinism space 303
need not be the same as someone else's. I have my own point
of view, and I therefore experience only certain aspects of
the thing and its relations to the rest of the world. (This is
what makes it possible for Frege to distinguish the Sinn of a
referring expression from its Bedeutung. See 'The Thought, a
Logical Enquiry', in Philosophical Logic, ed. P. F. Strawson,
for Frege's most mature published thought on this topic.)
However, I can, and you can, refer to my point of view, the
aspects I am aware of, etc. That is, we can both refer to the
object's 'mode of presentation' to me. But this again will be
something I refer to from a different viewpoint: if Z is the
original thing referred to, and Y is its mode of presentation
to me, then Y, like Z can be referred to by other people, but,
like Z, Y will also have a unique mode of presentation to me,
call it X. Again, I can refer to X, and so can you. By always
insisting that whatever we refer to or discuss publicly, there is
always something more, a point of view, an aspect, a mode of
presentation, uniquely underlying my manner of referring to
it, I adopt what might be called the strategy of always
pointing nearer to self.
The idea of a private, inner, domain,
accessible to nobody but oneself and identifiable to oneself
by a 'private ostensive definition', seems to be an idea arrived
at by postulating a limiting case defined by successive
application of this strategy. Note that I am not saying that
this concept is confused, incoherent, or whatever: I regard it
as an important fact about our language, thought and
experience that it makes this strategy possible, and any
philosophical system or theory of language which rules it out
is to that extent descriptively inadequate. (Even the limiting
case can perhaps be made respectable by defining it as the
union of all the 'modes of presentation' of objects to the
person in question.)
However, this very strategy is available to a robot
satisfying my conditions and able to represent, and therefore
think about, its relation to the things it perceives and refers
to. So the possession of a private world of the sort under
discussion is, after all, entailed by the satisfaction of
conditions like the ones I have formulated, even though it is
not mentioned explicitly.
At this point some philosophers will argue that my

304 space Determinism
discussion fails to give an adequate account of the ontological
of a mind and its contents. I can only reply that my
attempts to follow discussions of ontological status have so
far left me completely unable to grasp what the problem is,
that is, unable to see what there is to talk about, over and
above the sorts of issues I have discussed here.
I have tried to show (1) that the thesis (P) is empirical and
therefore not amenable to philosophical refutation; (2) that
it does not imply that mental phenomena are identical with,
or composed or, or reliably inductively correlated with
physical phenomena; (3) that it does not imply that human
actions have purely physical explanations; (4) that it does
not imply that mental events and processes can have no
causal influence on our actions. In addition, I have tried to
show how it is possible for our psychological concepts to get
a grip on a physical system, by describing conditions which
justify their application and which could be satisfied by a
physical system. In particular, I have tried to show how such
a system might, like a human being, have its own private,
inner experience.
I originally hoped to conclude with a discussion of the
claim that (P) implies that all deliberation is pointless or
impossible, that there is no such thing as moral responsibility, and that moral assessment of human actions in impossible. I do not think that (P) implies any of these things, but this paper is already too long, so I leave these topics untouched. No doubt readers will be able to predict how I would deal with them.

Note added 29 Dec 2005:

The original publication included a response to my paper, written before the conference, by two psychologists, George Mandler (UCSD) and William Kessen (Yale), entitled 'The appearance of free will' (pages 305 to 324), followed by a commentary by Alan R. White (Philosopher, Hull University), entitled 'Chairman's Remarks' (pages 325 to 330). Then followed (pages 331 to 339) several short discussion points submitted by people attending the conference (Sloman, Philippa Foot, Anita Gregory, Les Holborrow, Donald MacKay, Robin Attfield, Sloman), and finally a set of Concluding Remarks by Mandler and Kessen (pages 340 to 342) and Sloman (pages 343-7).
My own contributions to the discussion are below. I have not included the contributions of other authors partly because of copyright worries and partly for lack of time. However it is worth noting that Alan White defended the mind-brain identity thesis against my argument that the relation between intentional action and the corresponding physical process was a three-termed relation, and I accept this criticism in my discussion, though not the identity thesis.

Discussion space 331
Professor White is perfectly correct in finding fault with my
attempt to prove that actions and mental processes were
neither identical with nor composed of physical behaviour. In
essence, my argument went: 'there is a three-termed relation
between actions and physical behaviour, whereas identity and
composition are two-termed relations, so actions and physical
behaviour are not identical, etc.' This argument is not only
fallacious, but stupid, since it assumes that two objects
cannot be involved simultaneously in a two-termed and in a
three-termed relation. I can only apologise for wasting the
time of readers of the original paper over this point.
The source of my error was the tendency to talk of 'The
relation' as if only one relation existed between actions and
physical behaviour. Clearly there are many different relations,
as White observes in his paragraph (a). Yet he continues
to exhibit the same tendency as led me into error, for
instance in the opening sentences of his paragraphs 1) and 2).
I should like to comment on Professor Mandler and Professor Kessen's curious idea that a belief in the doctrine of free will is useful, although the doctrine is false. What they mean by 'the doctrine of free will' in this context is not that human choice is a reality, for that they think true. The 'false' b u t 'useful' belief is that choice is not determined. Professor Mandler and Professor Kessen say that 'under this doctrine' a man will be likely to try to maximise the beneficial effects of a choice; but why he should be more likely to do this if he believes in indeterminism is quite unclear. Among the factors 'determining' a man's choice the authors list motives. Why should a belief in this 'determinism' bring a man to abandon one particular motive?
Note added 29 Dec 2005:
White insists in his paragraph 1) that there is a distinction between behaviour of people including blushing, gasping, and believing, and behaviour of bodies. In his paragraph 2) he makes the important point that there is not just one mind-body relation but a variety of different relationships that need to be studied piecemeal. E.g. he suggests that the relation between sensations and brain processes may be unlike the relation between thoughts and neurological processes. This is very close to the point I was trying to make.
Various commentaries followed my note which are omitted here.

Discussion space 338
Mr Attfield's comments are based on the assumption that I
was talking about freedom, (which I don't think I ever
mentioned), and that I was trying to decide whether sometimes
human agents could have acted otherwise, which I
regard as an ill-formed problem. In order to refute my
supposed claims on these matters, he tries to argue that if
physicalism (as I defined it) is true, then 'the psychological
antecedents of my body's movements are thus redundant in
the prediction and explanation of those movements'. He does
not appear to realise that this conclusion is little more than a
reformulation of the physicalist premise presented as an
empirical hypothesis in section B of my paper. The premise
states that all physical behaviour of human bodies (and their
parts) conforms to current physical theory. I wrote that this
was meant to imply that in so far as the physically
describable movements can be explained and predicted they
can be explained and predicted in purely physical terms. So
psychological antecedents are obviously redundant in such
explanations and predictions. This is far from being
incompatible with anything I asserted. It does, however, leave
open the possibility, mentioned in the fourth last paragraph
of my section D, that there might be a different set of
premises, equally capable of predicting and explaining those
movements, in which the mention of psychological antecedents
was not redundant.
It seems that Attfield's main problem is whether human
agents sometimes could have acted otherwise. The answer is

Discussion space 339
obviously 'yes, they could have', just as it is obvious that
some physical mechanism could have behaved otherwise. For
instance, there could have been more petrol in the tank, in
which case the engine would not have spluttered to a halt
when it did. To produce a serious philosophical problem
about whether human agents could have acted otherwise, one
must specify a set of conditions supposed to remain fixed.
But what conditions? If physicalism (as defined in my paper)
is correct, then in theory one can always find some physical
specification of a set of conditions from which one can infer
with the aid of physical theories that (apart from quantum
indeterminacy) no physical process could have occurred in
those conditions other than what did occur. It is not clear
whether Mr Attfield finds this conclusion unpalatable or
rejoices in it, but it certainly seems to disturb some people
and I have tried to diagnose the unpalatability as due, in part,
to a mistaken assumption that the conclusion implies that
human actions can be fully explained in physical terms and
that beliefs, hopes, wants, fears, moral ideals and the like
cannot influence actions. My paper attempted to refute the
assumption. (The argument of my paper could be rejected by
showing that Professor White's enormously hospitable empirical
identity relation transmits explanatory force without any
explicit additional premises being needed. This far from

Concluding Remarks space 343
Finally, I should like to point out that I grow increasingly
convinced that all debates about determinism, free will and
the relations between mind and body, between actions and
movements, between mental processes and brain processes,
and so on are a waste of time until we have a much clearer
and more detailed and systematic characterisation of what
sorts of things agents, actions, decisions, thoughts, beliefs,
desires, and so on are. This characterisation will not come
from introspection, nor from piecemeal hacking away at the
puzzles that analytical philosophers are so fond of, nor from
psychological experiments, but from a sustained effort to
arrive at a new more perspicuous representation of a human
being which accounts for the fine-structure and the variety of
the enormous range of facts about human abilities and
possibilities that we all know and constantly take for granted
in our daily social interactions. These common-sense facts
have to be collected and organised in a systematic way so as
to provide a basis for constructing and testing a theory of the
kind of mechanism a human mind is.
The most penetrating advances in the development of
powerful new means of representing aspects of mind are
being made by those who attempt to formulate their theories
in computer programmes. Practitioners of the discipline of
Artificial Intelligence have been forced to develop and test all
sorts of new tools for representing aspects of mental abilities,
and the study of its literature is indispensable for anyone
interested in characterising human mental abilities. (One of
the most important, and most accessible, contributions so far
is T. Winograd's M.I.T. Ph.D. thesis, 'Procedures as a
representation for data in a computer program for under-
standing natural language'. This has appeared in the journal
Cognitive Psychology, January 1972, and has been published
as a book by Academic Press and Edinburgh University
Of course, such programming models will be inadequate in
all sorts of ways for some time yet, but the inadequacies are
rapidly discovered and (not quite so rapidly) attended to.
When we have a better idea of what sorts of things can be

Concluding Remarks space 344-5
Diagram from Pages 344-5 flowchart from pages 344-5

Concluding Remarks space 346
achieved by computer programmes (a new type of
mechanism) and how they are related to the computers
which contain them (an old type mechanism), we shall be in
a much better position to ask sensible questions about the
relations between mental and bodily phenomena, and about
free will and determinism.
For instance, a not very deep analysis of common-sense
knowledge about what sorts of processes a person can go
through in performing a variety of tasks, including solving
problems, playing games, constructing models from a
'Meccano' kit, explaining accidents, or reading a letter in
obscure handwriting; together with analysis of the meanings
of words and phrases like 'careful', 'rash', 'reckless', 'atten-
tive', 'alert', 'done from habit', 'learning from experience',
'trial and error', 'bear in mind', 'intended', 'intentional', etc.,
reveals that even in fairly mundane forms of human activity
the range of possibilities for mental processes is at least as
rich as the range represented by all the routes through the
accompanying flow-chart (Fig. 1). Moreover, which of the
possible routes is taken at any stage is normally determined
by the sorts of processes crudely indicated by the wording in
the boxes, yet also subject to higher levels of control based
on an awareness of what is going on and the results of tests
carried out by the 'monitors' mentioned in box 2. (Psycho-
logists please note: this chart is not offered as a new
psychological theory, merely as a convenient and fairly
economical summary of a large number of fairly obvious
common-sense facts.)
It can be argued that a mechanism generating at least the
range of possibilities expressed in the flow chart (with all
sorts of further complexities hidden in the boxes of the
chart) is minimally required for any system which can behave
with the kind of intelligence quite obviously exhibited by
human beings of all ages and many other animals (e.g. the
chimpanzees described in W. Kohler, The Mentality of Apes).
For a system with this range of possibilities inherent in it
there is obviously ample application for the concept 'could
have done otherwise'. If this is what freedom of the will is
about, then any intelligent system must have freedom of the
will. In this sense talk of freedom of the will is by no means

Concluding Remarks space 347
'inherited word play' that 'can be safely put aside' as Mandler
and Kessen suggest. Older exemplars of mechanisms, such as
the solar system, steam engines, and control mechanisms with
feedback loops, were clearly unable to generate this rich kind
of range of possibilities and so it used to seem obvious that
nothing describable as a mechanism could underly the kind
of thing we all know the human mind to be; and moreover
any suggestion that such mechanisms might adequately
model our minds was unpalatable on account of the implied
restrictions on possibilities for human choice. The only
previously known mechanisms capable of generating a rich
enough range of possibilities were meaningless agglomerations
of randomly related items, like the molecules of a gas or
perhaps a vast collection of roulette wheels. There was always
therefore an unhappy tension between excessively rigid
deterministic models and excessively purposeless random
No computing system known to me has the rich range of
possibilities for purposive action expressed in the chart,
though a superficial reading of Winograd's thesis mentioned
above may give the impression that his programme has.
However, it seems clear that programming languages, with
their facilities for expressing conditions under which dif-
ferent processes occur, and computing systems with their
potential for rapid, goal-directed, changes of complex inter-
nal structures, together provide new tools for thinking about,
and building and testing, new mechanisms which avoid both
extremes. Among the problems still to be solved, however, is
the problem of finding means of expressing and storing vast
ranges of very varied kinds of 'knowledge' in forms which
make them readily accessible when they are relevant to
current purposes and contexts and also readily modifiable in
the light of new information or the discovery of internal
inconsistencies, etc. (Compare boxes 2, 8 and 15 of the
flow-chart.) Here lie rich new pastures for philosophers and
psychologists interested in concepts like 'belief, 'skill',
'habit', 'association of ideas', 'learning', 'memory', etc.
To argue in advance that such attempts to represent
human mental abilities are futile because of the nature of the
physical processes known to underly computing systems, as

Concluding Remarks space 348
Herbert Dreyfus attempted to do in his paper, is, in the
current state of ignorance about what can and cannot be
programmed, like arguing that human brains could not
possibly provide a basis for human behaviour because of the
nature of the atoms and molecules of which they are
Similarly, in the current state of ignorance about what
sorts of powers can or cannot be programmed into com-
puters, about 99 per cent of philosophical discussion of
problems about the relation between mind and body and
about the extent to which human actions are or are not
determined is pointless.1 This applies to my own paper.
1 Several of the points made here can be found in Marvin Minsky's introduction to
Semantic Information Processing, edited by him. (M.I.T. Press, 1968)