The identity of working-memory and long-term memory representations follows from many lines of evidence. However, the data provided by Ruchkin et al. are hardly compelling, as they make unproved assumptions about hypothetical generators. We cite studies from our lab in which congruent slow-wave topographies were found for short-term and long-term memory tasks, strongly suggesting that both activate identical cell assemblies.

Ruchkin et al. ascribe a pivotal role to long-term memory representations and binding within working memory. Here we focus on the interaction of working memory and long-term memory in supporting on-line representations of experience available to guide on-going processing, and we distinguish the role of frontal-lobe systems from what the hippocampus contributes to relational long-term memory binding.

The view that short-term memory should be conceived of as being a process based on the activation of long-term memory is inconsistent with neuropsychological evidence. Data from brain-damaged patients, showing specific patterns of impairment, are compatible with a vision of memory as a multiple-component system, whose different aspects, in neurologically unimpaired subjects, show a high degree of interaction.

As revealed by standard neuropsychological testing, patients with damage either to the frontal lobe or to the hippocampus suffer from distinct impairments of working memory. It is unclear how Ruchkin et al.'s model integrates the role played by the hippocampus.

In their target article, Ruchkin et al. propose sustained neuronal interaction of prefrontal and posterior cortex involved in memory-storage mechanisms with respect to electrophysiological findings on the relationship of short-term and long-term memory processes. We will evaluate this claim in light of recent evidence from our laboratory on EEG coherence analysis of memory processes accompanying language comprehension.

The goal of our target article is to establish that electrophysiological data constrain models of short-term memory retention operations to schemes in which activated long-term memory is its representational basis. The temporary stores correspond to neural circuits involved in the perception and subsequent processing of the relevant information, and do not involve specialized neural circuits dedicated to the temporary holding of information outside of those embedded in long-term memory. The commentaries ranged from general agreement with the view that short-term memory stores correspond to activated long-term memory (e.g., Abry, Sato, Schwartz, Loevenbruck & Cathiard [Abry etal.], Cowan, Fuster, Grote, Hickok & Buchsbaum, Keenan, Hyönä & Kaakinen [Keenan et al.], Martin, Morra), to taking a definite exception to this view (e.g., Baddeley, Düzel, Logie & Della Sala, Kroger, Majerus, Van der Linden, Colette & Salmon [Majerus et al.], Vallar).

I will present evidence that nature does not optimize in the sense of Fermat's principle of least time, contrary to what Schoemaker's unintentionally ambiguous exposition might suggest. First, Huygens' principle, an alternative nonteleological account of Snell's law, is outlined. Second, I confront Fermat's principle with a substantive conceptual problem.

How should we assess the appeal of multiple scientific theories when they can all explain a particular empirical phenomenon of interest? We contrast Huygens' and Fermat's explanations of the law of refraction of light and find that neither dominates the other when considering multiple criteria for assessing the overall appeal of a scientific theory. The absence of teleology in Huygens' account is a strong plus compared to Fermat's. But Huygens' wave theory scores less well with respect to other desiderata for a scientific theory. In this case, there does not appear to be a clear winner, nor need there be one.

Byrne & Hilbert (B&H) argue that colors are reflectance properties of objects. They also claim that a necessary condition for something's being a color is that it causally explain – or be causally implicated in the explanation of – our perceptions of color. I argue that these two positions are in conflict.

Byrne & Hilbert (B&H) give some excellent replies to the objections to realism about color. However, the particular form of realism they propose, based on opponent processing, prompts several challenges. Why characterize a color by its tendency to produce an intermediate brain signal, rather than in terms of the final effect – either a perception or a neural substrate for it? At the level of the retina, and even of the cortex, there are processes that partly parallel the structure of color experience; but the correspondence is not exact. Must we assume that there is any place in the brain where an exact structural correspondence is found? At the level of psychophysical functioning, there is indeed opponency; but it is not clear that this gives us the kind of type-reduction that B&H want.

The disagreement between “color realists” and “color eliminativists” is better seen as a disagreement over pedagogical policies, about how best to satisfy lay curiosity about “what color is,” than as a clash of substantive theories. To suppose otherwise is to endow the ordinary language term “color” with more authority than it can bear.

Byrne & Hilbert (2003; henceforth B&H) do not adequately explain how it is that phenomenal colors are physical colors, as their physicalism claims. This explanation requires more characterization of the relationship between the epistemology and nature of color than B&H provide. With this characterization, we can see that a physicalist need not accept unknowable color facts, as B&H do.

Color experiences have representational content. But this content need not include a propositional component, particularly for reflectance physicalists such as Byrne & Hilbert (B&H). Insisting on such content gives primacy to language where it is not required, and makes the extension of the argument to nonhuman animals suspect.

Byrne & Hilbert (B&H) combine physicalism about color with intentionalism about color experience. I argue that this combination leads to an “error theory” about color experience, that is, the doctrine that color experience is systematically illusory. But this conflicts with another aspect of B&H's position, namely, the denial of error theory.

Our reply is in four parts. The first part, R1, addresses objections to our claim that there might be “unknowable” color facts. The second part, R2, discusses the use we make of opponent process theory. The third part, R3, examines the question of whether colors are causes. The fourth part, R4, takes up some issues concerning the content of visual experience.