The implicit-explicit distinction is applied to knowledge representations. Knowledge is taken to be an attitude towards a proposition which is true. The proposition itself predicates a property to some entity. A number of ways in which knowledge can be implicit or explicit emerge. If a higher aspect is known explicitly then each lower one must also be known explicitly. This partial hierarchy reduces the number of ways in which knowledge can be explicit. In the most important type of implicit knowledge, representations merely reflect the property of objects or events without predicating them of any particular entity. The clearest cases of explicit knowledge of a fact are representations of one's own attitude of knowing that fact. These distinctions are discussed in their relationship to similar distinctions such as procedural-declarative, conscious-unconscious, verbalizable-nonverbalizable, direct-indirect tests, and automatic-voluntary control. This is followed by an outline of how these distinctions can be used to integrate and relate the often divergent uses of the implicit-explicit distinction in different research areas. We illustrate this for visual perception, memory, cognitive development, and artificial grammar learning.

Many neuroscientists and philosophers endorse a view about the explanatory reach of neuroscience (which we will call the neuron doctrine) to the effect that the framework for understanding the mind will be developed by neuroscience; or, as we will put it, that a successful theory of the mind will be solely neuroscientific. It is a consequence of this view that the sciences of the mind that cannot be expressed by means of neuroscientific concepts alone count as indirect sciences that will be discarded as neuroscience matures. This consequence is what makes the doctrine substantive, indeed, radical. We ask, first, what the neuron doctrine means and, second, whether it is true. In answer to the first question, we distinguish two versions of the doctrine. One version, the trivial neuron doctrine, turns out to be uncontroversial but unsubstantive because it fails to have the consequence that the nonneuroscientific sciences of the mind will eventually be discarded. A second version, the radical neuron doctrine, does have this consequence, but, unlike the first doctrine, is highly controversial. We argue that the neuron doctrine appears to be both substantive and uncontroversial only as a result of a conflation of these two versions. We then consider whether the radical doctrine is true. We present and evaluate three arguments for it, based either on general scientific and philosophical considerations or on the details of neuroscience itself, arguing that all three fail. We conclude that the evidence fails to support the radical neuron doctrine.

A biological neuroscientific theory must acknowledge that the function of a neurological system is to produce behaviors that promote survival. Thus, unlike what Gold & Stoljar claim, function and behavior are the province of neurobiology and cannot be relegated to the field of psychological phenomena, which would then trivialize the radical doctrine if accepted. One possible advantage of adopting such a (correctly revised) radical doctrine is that it might ultimately produce a successful, evolutionarily based, theory of mind.

Logical problems inherent in claims that biological neuroscience can ultimately explain mind are not anomalous: They result from underlying social interests. Neuroscientists are currently making a successful bid to fill a vacuum of authority created by the demise of Freudian theory in popular culture. The conflations described in the Gold & Stoljar target article are the result of alliances between certain apologist-philosophers, neuroscientists, and institutions, for the purpose of commanding authority and resources. Social analysis has a role to play in addressing logical issues in the philosophy of neuroscience.

Two radical neuron doctrines must be distinguished, strong and weak. Gold & Stoljar direct much of their attack at the former, but the Churchlands hold only the latter. The weak radical neuron doctrine remains a serious possibility.

It seems that I often say things that might mistakenly be thought to identify me as an adherent of the radical neuron doctrine. I take the opportunity to explain my position more clearly and argue that many apparent conflations of the radical and trivial neuron doctrines are merely the result of misunderstanding what is meant when neuroscientists talk about the relations between different levels of description. It follows that there may be considerably fewer followers of the radical doctrine than Gold & Stoljar suggest.

Gold & Stoljar argue persuasively that there is presently not a good case for the “radical neuron doctrine.” There are strong reasons to believe that this doctrine is false. An analogy between psychology and economics strongly throws the radical neuron doctrine into doubt.

I argue that Gold & Stoljar's “trivial neuron doctrine” is not in fact trivial. Many familiar positions in the philosophy of mind run afoul of it, and it is unclear that even those whom Gold & Stoljar identify as adherents of the trivial neuron doctrine can be comfortably described as such.

The trivial neuron doctrine (TND) holds that psychology merely depends on neurobiology. The radical neuron doctrine (RND) goes further and claims that psychology is superfluous in that neuroscience can “replace it.” Popular among RND notions of “replacement” is “reduction,” and in our commentary we challenge Gold & Stoljar (G&S) to make clear their distinction between merely depends on (TND) and is reducible to (RND). G&S give us a TND–RND distinction that is a distinction without a difference; a defensible TND–RND distinction must have a metaphysical basis. We suggest a denial of compositionalism as such a basis.

The history of the natural sciences repeatedly shows that the unification of a higher level theory with a lower level theory by reduction does not eliminate the need for the higher level theory nor preclude its further development, leading to changes in the understanding of the lower level. The radical neuron doctrine proposes that the future science of psychology or linguistics will derive principally from the evolution of understanding at the neural level and not from current theories based on the observation of behavior. It is far more likely that the two bodies of theory will coevolve in semiautonomous fashion.

My focus is on the inability of neuron doctrines to provide an explanatory context for aspects of consciousness that give rise to the mind–body and other minds problem(s). Neuroscience and related psychological sciences may be viewed as richly contributing to our taxonomic understanding of the mind and conditions underlying consciousness, without illuminating mind–body and other minds perplexities.

As presently implemented, the neuron doctrine (ND) portrays the brain's neurons and chemical synapses as fundamental components in a computer-like switching circuit, supporting a view of brain = mind = computer. However, close examination reveals individual neurons to be far more complex than simple switches, with enormous capacity for intracellular information processing (e.g., in the internal cytoskeleton). Other poorly appreciated factors (gap junctions, apparent randomness, dendritic-dendritic processing, possible quantum computation, the living state) also suggest that the ND grossly oversimplifies neuronal functions. In the quest to understand consciousness, the presently implemented ND may throw out the baby with the bath water.

Gold & Stoljar's “trivial” neuron doctrine is neither a truism in cognitive science nor trivial; it has serious consequences for the future direction of the mind/brain sciences. Not everyone would agree that these consequences are desirable. The authors' “radical” doctrine is not so radical; their division between cognitive neuroscience and neurobiology is largely artificial. Indeed, there is no sharp distinction between cognitive neuroscience and other areas of the brain sciences.

Gold & Stoljar argue that there are two (often confused) neuron doctrines, one trivial and the other radical, with only the latter having the consequence that non-neuroscientific sciences of the mind will be discarded. They also attempt to show that there is no evidence supporting the radical doctrine. It is argued here that their dichotomy is artificial and misrepresents modern approaches to understanding the neuroscientific correlates of cognition and behavior.

The element of truth in behaviorism tells us that some versions of a radical neuron doctrine must be false. However, the representational nature of many mental states implies that neuroscience may well bear on some topics traditionally addressed by philosophers of mind. An example is the individuation of belief states.

Gold & Stoljar reveal that adherence to the radical neuron doctrine cannot be maintained via appeals to scientific principles. Using arguments from (1) naturalism and materialism, (2) unification, and (3) exemplars, it is shown that the “mind-is-brain” materialism explicit in the trivial version of the neuron doctrine ultimately suffers the same theoretical fate. Cognitive science, if it is to adopt an ontology at all, would be better served by a metaphysically neutral ontology such as double-aspect theory or neutral monism.

I argue that the trivial neuron doctrine as characterized by Gold & Stoljar is not trivial; it appears to be inconsistent with property dualism as well as some forms of functionalism and externalism. I suggest that the problem is not so much with the particular way in which Gold & Stoljar draw the distinction as with the unruliness of the distinction itself. Their failure to see this may be why they misunderstand the views of the Churchlands.

A thorough distinction between explanatory and descriptive concepts reveals a radical explanatory and a trivial descriptive doctrine in current neuroscientific research. The explanatory approach examines the neuronal substrates of the mind, whereas the descriptive one deals only with its correlates.

First, it is not clear from Gold & Stoljar's definition of biological neuroscience whether it includes computational and representational concepts. If so, then their evaluation of Kandel's theory is problematic. If not, then a more direct refutation of the radical neuron doctrine is available. Second, objections to the psychological sciences might derive not just from the conflation of the radical and the trivial neuron doctrines. There might also be the implicit belief that, for many mental phenomena, adequate theories must invoke neurophysiological concepts and cannot be purely psychological.

The privileged position of neural activity in biological neuroscience might be justified on the grounds of the nonlinear and all-or-none character of neural firing. To justify the neuron doctrine in cognitive neuroscience and make it both plausible and radical, we must consider the supervenience of elementary mental properties such as qualia on neural activity.