What we are seriously skeptical about, however, is the idea that the results of scientific work done with purely materialist assumptions will add up to a complete picture of the human mind, simply by accumulating the results of normal incremental science. In other words, we highly doubt that we will get a complete theory of the mind simply by doing more of what we already know how to do. Materialists may accuse us of being pessimists in this respect. (And indeed we all need to be optimists when looking for funding for our research, or when explaining ourselves to the media.) But there are some big problems, too, well-known in the relevant literatures. The successes of cognitive science and neuroscience come from solving little, localized, well-defined problems. These are typically problems that arise at the periphery of the human mind, concerning either input functions like visual perception and language, or output functions like motor planning. For larger scale problems at the center of the human mind—reason, will, conceptual thought, and so on—progress has been far more limited, and severe new questions about integration arise. Cognitive science so far has made essentially no discernible progress on many of these issues. The list of widely acknowledged outstanding problems includes the following.
- What gives conscious experience its particular subjective character? How could electrochemical events in the brain (but not anywhere else, as far as we know) produce the taste of a lemon, the distinctive sound of a flute, or the pain of a toothache? (The problem of qualia.)
- How can our words and thoughts, understood as patterns of activity in the brain, be the sorts of things that have meaning, that refer to things we could never have direct contact with, that represent states of affairs that can be true or false? (By contrast, other naturally occurring things, like rocks, may bear the imprint of past events, but they are not true or false concerning those events; they simply are what they are. Of course, a rock can bear an inscription of some kind, which could be true or false, but we would only see it as that if we believed that it was but there intentionally, by something with a mind—not if it appeared “accidentally,” as the result of ordinary physical processes.) (The problem of intentionality.)
- How can we act (or at least think we act) in a way that flows out of freely made choices, which are neither predetermined nor random, but freely chosen, so that we are rightly held morally responsible for the consequences? (The problems of free will and morality.)
- How can we understand the human capacity to reason in a way that is truly rational, managing to figure out what is relevant to a particular problem or issue in an open-ended and holistic way—even when there is no simple way to tell in advance what kinds of information might be relevant to the problem—all in a finite amount of time? (The problem of abductive reasoning, alias the epistemic frame problem; see Fodor 2000.)
- How can the specific perceptual properties that are “recognized” by individual neurons (e.g. colors, shapes, textures) be integrated together, first into coherent perceived objects (e.g. fuzzy blue squares), and then into a rich overall perceptual experience that takes in many objects perceived through different sensory modalities? (The binding problem, the unity of consciousness.)
- How can stable bits of abstract knowledge be represented by the ever-shifting flux of electrical activity that we observe in the brain?
— Stewart Goetz, from The Soul Hypothesis, p. 8