1. BEHAVIORISM:
SKINNER AND DENNETT
Philosophy of Mind
Curtis Brown
Skinner's main target in Science and Human Behavior (New York: Free Press, 1953), and
also elsewhere, e.g. in Beyond Freedom and Dig nity (New York: Alfred A. Knopf, 1971),
is what he calls quot;mentalism,quot; namely the appeal to inner psychological phenomena in the
explanation of human behavior. What is wrong with mental notions in the explanation of
behavior? Many things, according to Skinner, among them these:
1. We cannot directly observe mental phenomena. As a result they are quot;inferential.quot; On
Skinner's view, this disqualifies them as scientific explanations of behavior. Skinner
appeals to this point at several places in our reading. In a discussion of psychoanalytic
theory, he writes: quot;any mental event which is unconscious is necessarily inferential, and the
explanation [which makes use of it] is therefore not based upon independent observations
of a valid causequot; (30 [39]; bracketed page references are to the excerpt from Science and
Human Behavior in Ned Block, ed., Readings in the Philosophy of Psychology, Cambridge:
Harvard Univ. Press, 1980). Later he makes a similar criticism of commonsense
psychological explanation, e.g. explaining why someone drinks water by saying he is
thirsty. Skinner writes, of this quot;explanation,quot; that: quot;if it means that he drinks because of a
state of thirst, an inner causal event is invoked. If this state is purely inferential--if no
dimensions are assigned to it which would make direct observation possible--it cannot
serve as an explanationquot; (33 [41]). At one point, Skinner even seems to identify
quot;inferentialquot; with quot;fictionalquot; (28 [38]).
Now, there is surely something valuable and important abou this. Invoking phenomena
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which we cannot directly observe in explanat ons of things we can observe is always risky.
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I do not mean risky in the sense that we may turn out to be wrong; virtually any scientific
claim is risky in that sense, including claims about things we can directly observe. The
more serious risk is that we will make claims which are really not testable at all, which
empirical evidence can never show to be mistaken because we can always fudge the theory
a bit to explain why the evidence was to be expected after all. To use Karl Popper's term,
the danger of quot;inferentialquot; states is that theories making use of them may not be falsifiable.
(Popper himself wrote of psychoanalysis: quot;those 'clinical observations' which analysts
naively believe confirm their theory cannot do this any more than the daily confirmations
which astrologers find in their practice.quot; Popper, Conjectures and Refutations: The Growth
of Scientific Knowledge (New York: Basic Books, 1962), pp. 37-38.) So we can read
Skinner as making the important po that when we invoke theoretical entities or
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phenomena we need to do so in such a way that the theory making use of them makes
predictions about observable phenomena which can be falsified.
But Skinner seems to take himself to have shown something much stronger than this,
namely that a scientific theory should not make use of inferred entities or phenomena at

2. all. And this seems much too strong a claim. If we restricted physics, or even archeology or
paleontology, to making use only of things that can be directly observed, we would deprive
ourselves of most of their most interesting results--and also of a good deal of their
predictive power. It often happens that the best theory which accounts for observed
phenomena and makes predictions about unobserved but observable phenomena makes use
of a good deal of theoretical apparatus for which our only evidence is inferential. An
analogy may be helpful in seeing this point. Imagine typing things into the keyboard of a
computer, observing the computer's responses, and trying to formulate hypotheses about
how the machine will respond to various future stimuli. Conceivably we could do this
without appealing to any hypotheses about how the machine is programmed, so that our
theory simply took the form of correlations between inputs and outputs. But it seems quite
clear that it will be far more useful to hypothesize about the machine's (internal, not
directly observable) program, using hypotheses about the program together with
information about inputs to formulate predictions about the machine's output. Now we may
not be quite like computers, but presumably the principles which govern our behavior are
at least as complex as those that govern a computer, so we may reasonably expect that
formulating hypotheses about our own internal states and processes will turn out to be the
most effective way of explaining and predicting our behavior. At the very least, it seems
clear that it would be a mistake to rule out a priori any theory which made use of such
hypotheses.
2. Mentalistic accounts are not genuinely explanatory. Skinner argues that many
supposed explanations are really just made up on the spot and do not provide a genuine
account of one's behavior. After giving a number of examples (e.g. one is confused because
his mind is failing; one is disorganized because his ideas are confused), he writes: quot;in all
this it is obvious that the mind and the ideas . . . are being invented on the spot to provide
spurious explanationsquot; (30 [39]).
Again, Skinner seems to be providing a useful warning: it would be a mistake to take such
offhand remarks as having much explanatory power. (But, for a defense of the view that
commonsense psychology does provide a fairly powerful explanat ry account of a good
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deal of our behavior, see the writings of Jerry Fodor, e.g. his Psychosemantics (MIT Press,
1987), Chapter One.) On the other hand, most such remarks are not even supposed to be
explanations of behavior; often they are just casual ways of describing it. The explanatory
emptiness of much of our ordinary talk about mental events is not evidence that mentalis tic
notions can find no place in a genuinely scientific account of human behavior.
3. Mentalistic explanations are typically redundant. Skinner claims that mentalistic
explanations really just restate the facts of behavior in more obscure language. He writes,
for example, that: quot;A single set of facts is described by the two statements: 'He eats' and
'He is hungry.' . . . A single set of facts is described by the two statements: 'He plays well'
and 'He has musical ability.'quot; (31 [39]). Here there seems to be at least a trace of the
linguistic thesis of philosophical behaviorism as exemplified by Carnap and, at one time,
Hempel. The idea seems to be that the mentalistic statements have the same meaning as the
behaviors that count as evidence for them. But 'He eats' and 'He is hungry' don't mean quite
the same thing (either could be true without the other being true), and in cases where
mentalistic notions are doing more theoretical work it will be even clearer that there is no
straightforward translation from mentalistic talk into behavioristic talk.

3. 4. The quot;middle linkquot; argument. Skinner suggests that, since the inner mental states which
are supposed to explain behavior are themselves determined by external stimuli, they can
safely be ignored: we can leave out the middleman and simply study the relations between
stimuli and behavior. quot;Unless there is a weak spot in our causal chain so that the second
link is not lawfully determined by the first, or the third by the second, then the first and
third links must be lawfully related. If we must always go back beyond the second li k for
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prediction and control, we may avoid many tiresome and exhausting digressions by
examining the third link as a function of the firstquot; (35 [42]).
At first sight, this looks very reasonable. If S determines M and M determines R, then S
indirectly determines R: why not just consider the relationship between S and R, ignoring
M? Dennett's computer analogy, which I mentioned above, is helpful here. It may be that
the most effective way of explaining the relationship between S and R is by way of
hypotheses about the nature of M. What is quot;hard-wiredquot; in aside (this is comparable to
human genetic makeup), how the machine is programmed is determined by inputs to the
machine and, together with current inputs, determines the machine's output: but trying to
predict output on the basis of input alone, without hypotheses about the machine's internal
states and processes, is likely to be a disaster. It is worth mentioning Noam Chomsky's
discussion of this point early in his review of Skinner's Verbal Behavior (in Language vol.
35 no. 1, 1959; reprinted in Ned Block, ed., Readings in the Philosophy of Psychology
Volume 1 (Harvard, 1980)): quot;Anyone who sets himself the problem of analyzing the
causation of behavior will . . . concern himself with . . . the record of inputs to the organism
and the organism's present response, and will try to describe the function specifying the
response in terms of the history of inputs. . . . The differences that arise between those who
affirm and those who deny the importance of the specific 'contribution of the organism' to
learning and performance concern the particular character and complexity of this functionquot;
(49).
5. Mentalistic explanations are homuncular. Skinner in a number of places objects to
mentalistic explanations that they in effect invoke a little person or homunculus wi h all the
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same abilities that the ordinary person has. quot;The inner man is regarded as driving the body
very much as the man at the steering wheel drives a carquot; (29 [38]). Explaining the behavior
of a person by appealing to a little person inside the head, quot;drivingquot; the body, clearly does
not accomplish anything, since the actions of the homunculus are just as much in need of
explanation as the actions of the person were originally. This is the criticism Dennett takes
most seriously; Dennett's version is: quot;Since psychology's task is to account for the
intelligence or rationality of men and animals, it cannot fulfill its task if anywhere along the
line it presupposes intelligence or rationalityquot; (Dennett, quot;Skinner Skinned,quot; in Dennett,
Brainstorms, Cambridge: MIT Press, 1978, p. 58).
All right. There's clearly something to this. But notice two things. (1) It clearly doesn't
accomplish anything to quot;explainquot; someone's behavior by reference to a quot;homunculusquot; just
as smart as the original person. But it doesn't follow that homunculi are useless. They may
nevertheless accomplish something if they are dumber than the original person. We might
be able to understand the capacities of a person in terms of the interactions of a number of
agents each of which has simpler capacities than the orig person; we might then explain
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each of these dumber agents in terms of a system of still dumber agents, and so on until at
the very bottom level we have something so simple it can be understood in terms of

4. neurons firing or something of the sort. This kind of explanation is familiar from computer
science: a big complicated program may have a number of subroutines which can be
thought of as agents dumber than the original program; these subroutines may themselves
be decomposed into more basic routines, and so on, until at the bottom we reach circuits
opening and closing. For the view that somethi g like this is the best way to understand the
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human mind, see e.g. Marvin Minsky, The Society of Mind; see also some of Dennett's
essays in Brainstorms, especially quot;Artificial Intelligence as Psychology and as
Philosophy.quot;
(2) The second thing to notice is that even if we must ultimately explain intelligence or
rationality in terms that don't presuppose intelligence or rationality, it doesn't necessarily
follow that intelligence and rationality should not be appealed to at all, or that they are
ultimately unreal. Rather than showing that we aren't really rational, such an explanation
might instead show what rationality consists in, might show what it is to be rational. This is
Dennett's main point in quot;Skinner Skinned.quot; Dennett argues that thereis a crucial difference
between explaining and explaining away (65). If our explanation of apparently rational
behavior turns out to be extremely simple, we may want to say that the behavior was not
really rational after all. But if the explanation is very complex and intricate, we may want
to say not that the behavior is not rational, but that we now havea better understanding of
what rationality consists in. (Compare: if we find out how a computer program solves
problems in linear algebra, we don't say it's not really solving them, we just say we know
how it does it. On the other hand, in cases like Weizenbaum's ELIZA program, the
explanation of how the computer carries on a conversation is so simple that the right thing
to say seems to be that the machine isn't really carrying on a conversation, it's just a trick.)