Tuesday, 20 March 2007

McDowell’s Direct Realist Reply to Scepticism

McDowell’s claim that in veridical cases of perception objects are “immediately present to the mind” has earned him the title of direct realist. Direct realism is the thesis that what we perceive are not merely appearances (insert: sense data, veil or ideas or whatever else suits your fancy) but rather objects themselves.

Direct realism can be used against arguments for external world scepticism (EWS) of of the following form:
P1: Our EW beliefs are based on sense data beliefs
P2: Sense data beliefs cannot justify EW beliefs
EWS: Our EW beliefs are not justified
The direct realist resists EWS by rejecting P1. There are two senses in which the direct realist can maintain that our EW beliefs are not based on sense data beliefs. First, they can deny that there are such things as sense data beliefs. This is certainly true in McDowell’s case since his rejection of the highest common factor view, a fortiori, includes the eschewal of any such mediating beliefs. Second, if we interpret the locution ‘based on’ in a strong inferential sense, then a direct realist may insist that our EW beliefs are not inferred from any other beliefs at all but are rather immediately grasped by the perceiving subject.

However, the locution ‘based on’ need not be taken in this strong inferential sense. A sceptic may insist that there can be a weak sense of ‘based on’ that is non-inferential. For example, we may interpret the phrase ‘based on’ in causal terms. Putatively, it seems undeniable that our EW beliefs are causally based on appearances or sense impressions. According to an empirical-psychological account of vision, the act of seeing an object involves several complex physiological processes. Moreover, we never see objects themselves, but merely the light bundles reflected off an object. Thus, there are several causal intermediaries between our EW beliefs and the objects in the eternal world. Thus, our sceptical argument may be reformulated as follows:
P1*: Our EW beliefs are (causally) based on sensory appearances
P2*: Sensory appearances cannot justify EW beliefs
EWS: Our EW beliefs are not justified
Significantly, P1* does not assert that sensory appearances are the intentional object of our perceptual experience. For instance, by P1*’s lights we are free to view sensory appearances as the means rather than object of our perceptions. In other words, P1* merely asserts that sensory appearances form part of the causal chain linking our beliefs to the EW that gives rise to our beliefs. Thus, P1* can be construed along purely direct realist lines—to wit, we may hold P1* while simultaneously maintaining that objects themselves (and not some mental intermediary) are the intentional objects of our perceptions. Thus, even if we grant direct realism’s denial of an inferential intermediary, P1* still stands.

Unfortunately for the sceptic, this reply fails in the case of McDowellian direct realism. McDowell may gladly concede that the causal descriptions (with all its various intermediary steps) of empirical psychology are true. However, McDowell maintains that the empirical-psychological account is not only one available. In fact, McDowell draws on the Sellarsian idea of there being a sui generis “space of reasons” for precisely this reason. When McDowell describes perception as being direct, he is speaking in terms of the logical space of reasons, not in terms of the logical space in which the subject matter of empirical science falls. Things like photons or electrical impulses are  not of the right sort to act as a reason for one's beliefs. Trading on this ambiguity in the locution ‘based on’, McDowell may accept P1*, but point out that P1* cannot plausibly be combined with P2* in order to generate EWS.  P1* (explicitly) exploits the epistemically insignificant notion of being ‘causally’ based on, while P2* (implicitly) exploits the  epistemically significant notion of being ‘justificationally’ based on.  This equivocation in the explicit notion of "based on" in P1* and the implicit notion of "based on" in P2* prevents the inference from going through.

In sum, McDowellian direct realism is effective against sceptical arguments of a certain form. Specifically, sceptical arguments that ride on there being an inferential or causal intermediary between our EW beliefs and the objects we perceive are easily defeated by direct realist considerations. Of course,  arguments for EWS may take other forms as well.

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