The Empiricist Model

Bertrand Russell vacillated over the years, but in his great little book,

The Problems of Philosophy, he held that colors are in our own minds, just

as Berkeley and Hume thought, and that we infer the existence of phys- ical colors, physical shapes, and so on, from the properties of these mental entities, and this is a standard empiricist view (sometimes dolled up with the idea that the inferences are “unconscious,” or that we don’t really make them but it is enough that we could make them, if we were suffi ciently “rational”). Many have criticized this view on metaphysical and epistemological grounds, and with good reason, but today I want to look at this and the other two models I mentioned from the stand- point of psy chol ogy. From that standpoint, the immediate prob lem is that we obviously don’t make the sorts of inference that Russell described in The Problems of Philosophy— not unless we are Bertrand Russell! (Nor did he think we made them; in his view most people are utterly ignorant of their epistemological predicament.) Indeed, the idea that we make such inferences is incompatible with the traditional empiricist claim that ( unless we have been educated by phi los o phers like Russell) we simply proj ect our qualia onto the external world without realizing that there is a difference between those objective properties and our qualia.

What about the dolled-up version, according to which we make such inferences “unconsciously”? At best, this is a hypothesis about subper- sonal mechanisms, and I believe that we also need an acceptable personal- level description of perception, and not only an account of the subpersonal mechanisms that subserve perceiving, thinking, deciding, and so forth. But even at the subpersonal level, we now know of many more kinds of computation that the brain is capable of using than prop- ositional inference, so even as a subpersonal account, “unconscious in- ference from our sense data” is out of date.

Moreover, the inputs to the brain are not qualia, but not because qualia aren’t features of brain events (I believe that they are, and, in any case, they certainly supervene on brain events). The idea of qualia as inputs might have been at least partially vindicated had it turned out that Fodor’s “modularity” view, on which phenomenal appearances are simply outputs of perception- modules, turned out to be right. In that case qualia might be identifi ed with those outputs, and those outputs in turn identifi ed with the fi rst stage of cognitive pro cessing. But the consensus in neural science today favors a much more complicated story. On the modularity hypothesis, perception was supposed to be an entirely “bottom up” affair, but today it is becoming clear that that perception is both “bottom up” and “top down.” When I see a tomato, for example, many parts of the brain are involved, and interactions (reverberating circuits) take place between cortical and precortical functions. If there are “inputs” to the brain, they begin with the eyes— much earlier than the formation of “qualia.”

One might try to bypass this objection by adopting a dualistic view of the unconscious mind, and posit that while the inputs to the brain are neural stimulations, beginning in the eyes, the inputs to the uncon- scious mind are “ mental” qualia, but at this point all contact with both science and phenomenology would have been lost. The “unconscious inference” story was cutting edge psy chol ogy at one time,13 _{but it is not}

tenable as either personal level or subpersonal level psy chol ogy today. What about the version according to which the story about inferences from qualia to material objects is supposed to be a “rational reconstruc- tion”? When we make explicit the steps in a proof that are left implicit in a mathematics journal, for example, we are engaged in rational reconstruction, but in such a case the steps could have been made explic- itly to begin with (the article would simply have been boring to read). But to say why I believe that there is a computer in front of me as I type these words by (1) describing all the relevant “sense data” and (2) pro- viding an inference from all that information (assuming it exists, and assuming it could all be stated) to “ there is a computer in front of me” is not something I could really do. At best (and assuming we ignore all

13. H. L. Helmholtz, Handbuch der physiologischen Optik, vol. 3 (Leipzig: L. Voss, 1866); repr. 3rd ed., with extensive commentary by Allvar Gullstrand, Johannes von Kries, and Wilibald Nagel (Hamburg and Leipzig: L. Voss, 1896), 28–29.

the objections that critics of traditional epistemology have raised), all that the “rational reconstruction story” could show is that a person with literally superhuman capacities for phenomenological description, retention of information, and rapid reasoning would be justifi ed in believing that there is a computer in front of him or her, and not that persons like ourselves are justifi ed in our perceptual beliefs. Perhaps in such a case justifi cation is not needed— justifi cation comes to an end, as Wittgenstein said in On Certainty14_{— but providing such a justifi ca-}

tion was precisely the purpose of the “rational reconstruction”!