4. Formulating the DIA with and without the Re-identification constraint
The gist of DIA is easy to convey, but certain difficulties arise in stating precisely how the argument is supposed to present a problem for conceptualism. One of the central difficulties concerns whether DIA needs to be formulated in terms of a strong memory-based requirement on concept possession, the Re-identification constraint. In what follows, I’ll begin with the gist and then move on to formulations of DIA with and without the Re-identification constraint. Along the way I’ll make remarks about the Re-identification constraint and certain problems with it.
4.1. The gist of DIA
There exist color pairs sufficiently similar to be indiscriminable across a memory delay while sufficiently distinct to be discriminable when presented simultaneously (Perez–Carpinell, Baldovi, de Fez, & Castro, 1998; Raffman, 1995). So, for example, two paint chips presented side-by-side will be clearly and correctly distinguished as having distinct colors, but if presented one after the other, the viewer will be uncertain whether they have distinct colors. Though, for simplicity, I’ll just be focusing here on color, the point generalizes to aspects of vision other than color and also to other sensory modalities besides vision. There are thus a wide variety of stimulus pairs that are discriminable in simultaneous presentations but indiscriminable in serial presentations.
As Raffman (1995) argues, if we make certain natural assumptions concerning the relations of concepts to memory, then the existence of such stimulus pairs puts pressure on the suggestion that conceptual contents exhaust the contents of experience. Given certain connections between the conceptualized and the remembered and the recognized, then the existence of such stimulus pairs suggests that experience outstrips our concepts.
On the face of it, Raffman’s case against conceptualism may seem persuasive. Since the colors in question are simultaneously discriminable, that gives us reason to believe that there are corresponding contents of consciousness. Given certain assumptions about the relation of concepts to memory, the failure to discriminate these colors across a memory delay indicates that these conscious contents outstrip conceptual content.
It is clear that the gist of the argument involves two key assumptions: one concerning what’s experienced in the diachronic presentation of the diachronically indiscriminable colors and one concerning a memory constraint on concept possession. In working toward a more precise statement of the logical structure of the DIA, we can represent these two assumptions as two distinct premises. Additionally, we must include a premise concerning conceptualism—a thesis concerning the relation of concepts to conscious experience. And, of course, there must be some statement of the empirical finding concerning the failure of diachronic discrimination. The form of the argument then is the following four-premise argument. (We can state the argument in terms of two shades of blue, blue1 and blue2, that are synchronically distinguishable but not diachronically distinguishable, and are presented separately at two times, t1 and t2, respectively.)
(1) The Experience Assumption: Shade blue1 gives rise to a conscious experience with a phenomenal character at time t1 that is distinct from the phenomenal character of the conscious experience that the shade blue2 gives rise to at time t2.
(2) The Memory Constraint: In order to be in possession, at time t1 of a concept of blue1, one must be capable of remembering blue1 at the later time, t2.
(3) Conceptualist Assumption: If one has conscious experience of blue1 (a conscious experience with a phenomenal character distinct from the conscious experience of blue2 at time t2) at time t1, one must be in possession of a concept of blue1 at t1.
(4) An Interpretation of the Indiscriminability Data: Given the diachronic failure to discriminate the synchronically discriminable blue2 from blue1, blue1 was not remembered at t2.
(5) Anticonceptualist Conclusion: One can have a conscious experience of blue1 without being in possession of a concept of blue1 at t1.
4.2. The Re-identification constraint (RIC)
One strategy for resisting the DIA is to construe the memory constraint as an alleged a priori constraint on concept possession—the Re-identification constraint—and then to contrive armchair counterexamples to the constraint. This is what I take to be the main thrust of Chuard’s (2006) case against the DIA.
Chuard presents a case that for arguments against conceptualism based on fineness of grain to have their best chance at success, they need the premise concerning memory to be formulated as follows (p. 170):
[I]f a subject S possesses a concept C for a property f, S must be able to (i) identify some object o as f at time t; (ii) to identify some object o’ as f at time t+1; and (iii) to identify f at t+1 as the same property f as at t.
For an example of the sorts of armchair examples Chuard presents, consider this (p 181).
Suppose that the subject had recently lost her capacity for short-term and long-term memory about her personal life. She still has a very general knowledge about the world, but none about herself. Her general knowledge implies that she has not lost her conceptual skills – and is thus perfectly capable to identify triangles. In her situation, the subject will be completely unable to re-identify the newly presented triangle as the same shape she was earlier presented with. That is because she cannot remember anything about her past experiences. Still, by hypothesis, she can identify the shape in question as a triangle.
Chuard’s case of the amnesiac counts as a counterexample to the Re-identification constraint on the grounds that right before her amnesia, the amnesiac identified something as a triangle and at no later time is she able to re-identify subsequent shapes as the same one she saw on that earlier occasion. Perhaps those who are sympathetic to the Re-identification constraint will want to resist Chuard’s counterexample. But I want to here bypass the issue and just grant Chuard’s counterexample. I am more than happy to reject the Re-identification constraint as imposing an a priori constraint on concept possession. Regardless, I think that there is an empirical generalization that proponents of DIA may make a plausible appeal to, and thus still have a plausible case on their hands against conceptualism.
4.2. Formulating the DIA without the Re-identification constraint
To get a feel for the proper roles that notions of concepts and memory play in the DIA, it helps to begin with considerations of what, in general would explain a failure to diachronically discriminate two colors.
For any two colors that one fails to discriminate diachronically, there are two general possible explanations. One is that the failure is due to memory failure: upon presentation of the second color, one doesn’t adequately remember the first color and thus is not in a position to correctly discriminate the two. The other possible explanation is that the failure is due to perceptual failure: upon presentation of the first color, one does not adequately perceive it, and so even if one perceives the second color, one won’t be in a position to discriminate the two.
Memory-based explanations are plausible only under certain kinds of conditions. For example, if there is good reason to believe that the separate stimuli were both perceived and conceptualized under distinct concepts, then a failure to discriminate the colors is plausibly due to a memory failure only if the delay is quite long. Perceived colors differing with respect to differences we uncontroversially do have concepts for, say, red and blue, that straddle only a short delay, say the time it takes to turn a page, are easily diachronically distinguishable. However, with a really long delay (days, years) one may very well forget the first color and thus, on presentation of the second color, be
in absolutely no position to discriminate it from the first.
In contrast, memory-failure explanations seem implausible for very short delays, especially when the stimuli are conceptualized. And this is not to impose a hard-core Re-identification constraint on concept possession. Even if the Re-identification constraint has possible counterexamples, the following seems to be a well-supported empirical generalization: for very short delays, if one does conceptualize the stimulus, one tends to be able to remember it. Instead of viewing the Memory Constraint premise of DIA as depending on the Re-identification constraint, we can instead see it as following from the following empirical generalization:
(M): Relative to short time periods, if a stimulus is conceptualized then it is remembered.
Of course, an analogous generalization doesn’t hold for very long stretches of time. I can
conceptualize a passing stimulus as a man with a mustache, but it’s highly likely that this will be forgotten eventually in a few minutes, hours, or days. But when we look to shorter time periods, periods spanning just a few seconds, (M) seems highly plausible. Consider diachronic discrimination tasks comparing performance for words or written
characters in known and unknown languages. It is plausible to predict support for (M) in such tasks. And we can see this as consistent with the sorts of effects that psychologists chalk up to “depth of processing” (Craik & Lockhart, 1972).
We are in a position now to see DIA as depending not on a re-identification-based conceptual analysis of the concept of “concept,” but instead on the reasonable empirical generalization, (M). Shades blue1 and blue2, discriminable synchronically but not diachronically even across very short delays seem to give conceptualists a problem. Because of (M), we’d expect a conceptualized blue1 to be remembered long enough to support an appropriate comparison to blue2.
I turn now to present a case that, of the four premises of the DIA, the most questionable one is the Experience Assumption. I turn now to flesh out a case against the DIA that involves calling into question the Experience Assumption.