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The Existence of Mind-Independent Physical Objects

3. Phenomenalism as Parasitic on Realism

Book cover: The Web of Belief by W. V. Quine and J. S. Ullian

As we saw from the final two objections covered in the previous section, phenomenalists' rendering of statements about physical objects and experiences fail to yield a finite set of translation sentences in either direction of translation. The phenomenalist is unable to provide a convincing reason for why we should not expect such a finite set of translation sentences. The anti-phenomenalistic realist, on the other hand, is able to explain, in principle, why this should be so. Contra phenomenalism, there is a logical gap between 'physical object' statements and 'experience' statements. And this is because the form of experience that an observer has in a particular perceptual situation is a function not only of the properties of the physical object under observation, but also of the properties of the mediating substances, the neurophysiological state of the observer and the nomological link between the neurophysiological state and the experiential state.

For this same reason, there is a logical gap between common-sense or scientific physical theories and 'experience' statements. Physical theories only entail 'experience' statements once the theory is conjoined with theories about the properties of mediating substances, a theory of observation including a neurophysiological theory and psycho-physical linking laws (either in the form of identity laws or correlation laws), and statements about the initial conditions of the external objects and states of the observer. The mistake that analytic phenomenalists make is that of trying to pack the meanings of all of these auxiliary theories into the meaning of the term labelling the 'physical object' under observation or the particular physical theory under test.

In fact, the phenomenalist's analysis of 'physical object' statements turn out to be parasitic on the anti-phenomenalistic realist conceptual scheme outlined here. For how does the phenomenalist arrive at his subjunctive conditionals?[10] How does he, for example, work out the particular subjunctive conditionals that go to make up the meaning of the statement, 'Venus orbits the Sun'? Precisely by taking the laws of planetary motion, the laws of optics, the laws governing the reflective and refractive properties of the earth's atmosphere, the laws governing the operation of the human retina, the laws governing the neural processing of visual information and the psycho-physical linking laws (this list is not meant to be exhaustive), and then, by suitable permutations and combinations of the various constants corresponding to the various (infinite number of) initial conditions, finally deducing the expected perceptual experience under each initial condition.

Notice, firstly, that to work out the semantic content of 'Venus orbits the Sun' in 'experience' terms, the phenomenalist is using a realist conceptual scheme consisting of observer-independent physical processes. The experience of the observer is calculated to be the end result of a long chain of causal processes described in terms of physical theories that make no mention of the observer or experiences.

Secondly, it seems clear that for the phenomenalist to work out the semantic content of 'Venus orbits the Sun' in 'experience' terms, he must already know the meaning of 'Venus' and 'Sun' and 'orbit' in order for him to select correctly the relevant laws and be able to manipulate them, in conjunction with other laws, to achieve the desired 'translation'. Obviously, the phenomenalist selects primarily that set of laws (the laws of planetary motion) which contain as constants the terms 'Sun' and 'Venus', and which describe in mathematical form their spatial co-ordinates with respect to a time co-ordinate. It seems to me that 'Sun', 'Venus' and the other special terms of the theory gain their interpretation through the postulates of the theoretical system in which they are embedded, and this is how the phenomenalist knows their meaning.

The phenomenalist may admit that he had knowledge of the meanings of 'Venus', 'Sun' and 'orbit' prior to his phenomenalist translation, but that it was only partial knowledge. It is true, he will say, that the full meaning of these terms is given by the postulates of the laws of planetary motion, but, he will object, the meaning of these laws is exhausted by statements about possible experiences. However, the problem for the phenomenalist, once again, is that in working out the semantic content of the laws of planetary motion in 'experience' terms, he must use other physical and psycho-physical laws, which in turn must be interpreted in 'experience' terms by other laws, and so on.

In general, a phenomenalist interpretation of a natural law in 'experience' terms will need to specify particular observation conditions, measuring instruments, and so on, which will in turn require further interpretation, and so on ad infinitum. Not only will this translation procedure lead to an infinite regress, it will also lead to a vicious circle. Consider for a moment a phenomenalist interpretation of the laws of planetary motion. This translation will require the use of the laws of optics (in order to determine the positions of images of planetary bodies on the lenses of telescopes, for one). But conversely, a phenomenalist interpretation of the laws of optics requires the use of the laws of planetary motion (in order to determine the amount of bending of a light ray in the presence of a gravitational field, for one).

To avoid an infinite regress and a vicious circle, we must allow that the meanings of 'physical object' terms and physical theories are not defined primarily in 'experience' terms. 'Physical object' terms and the theories in which they are embedded only have observational import when conjoined with a whole host of other physical theories and psycho-physical linking laws. My point here then is this: the extent to which a phenomenalist uses a physical theory or theories to work out the meaning of a 'physical object' term or another physical theory in 'experience' terms, without first giving a full phenomenalist interpretation of the physical theory that he is using (which I have argued is, in principle, impossible), is the extent to which his phenomenalist interpretation is parasitic on an anti-phenomenalistic realist assumption.

The phenomenalist's acceptance of contingent subjunctive counterfactual conditionals thus presupposes an anti-phenomenalistic realist framework. However, because the realist can explain the truth of these counterfactual conditionals (which, for the phenomenalist, remain inexplicable at the physical level) in terms of the physical and psycho-physical theories from which they are derived, there is then no need to justify them in terms of Berkeley's God or an Absolute or some other 'ultimate reality' underlying the physical world.

The upshot of what I have said so far is that phenomenalistic idealism is untenable because our 'physical object' language is irreducibly realist at its conceptual core. If it is not already clear, then it should be clear by the end of the next section that phenomenalism construed not as a descriptive thesis about our actual 'physical object' language, but as a proposal for linguistic reform, is similarly untenable because of the conceptual and heuristic sterility of such a proposed language. The conclusion of this section, then, is that the realist's thesis a., that physical objects do not depend for their existence on being perceived or conceived by mind, is analytically true.

Footnotes

  1. [10] Here, I refer to counterfactual conditionals of the form, 'If it had been the case that A, then B' and 'If it were the case that A, then B', where the antecedent A is posited to be in fact false.

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