Much of the cognitive lies beyond articulate, discursive thought, beyond the reach of current computational notions. In Sketches of Thought, Vinod Goel argues that the cognitive computational conception of the world requires our thought processes to be precise, rigid, discrete, and unambiguous; yet there are dense, ambiguous, and amorphous symbol systems, like sketching, painting, and poetry, found in the arts and much of everyday discourse that have an important, nontrivial place in cognition.

Goel maintains that while on occasion our thoughts do conform to the current computational theory of mind, they often are -- indeed must be - vague, fluid, ambiguous, and amorphous. He argues that if cognitive science takes the classical computational story seriously, it must deny or ignore these processes, or at least relegate them to the realm of the nonmental.

As a cognitive scientist with a design background, Goel is in a unique position to challenge cognitive science on its own territory. He introduces design problem solving as a domain of cognition that illustrates these inarticulate, nondiscursive thought processes at work through the symbol system of sketching. He argues not that such thoughts must remain noncomputational but that our current notions of computation and representation are not rich enough to capture them.

Along the way, Goel makes a number of significant and controversial interim points. He shows that there is a principled distinction between design and nondesign problems, that there are standard stages in the solution of design problems, that these stages correlate with the use of different types of external symbol systems; that these symbol systems are usefully individuated in Nelson Goodman's syntactic and semantic terms, and that different cognitive processes are facilitated by different types of symbol systems.