Abstract

As a high school student, I rediscovered Hume’s problem of induction on my own. For a while, I was horrified. I thought, “We cannot know anything!” After a couple of weeks I calmed down and reasoned that there had to be something wrong with my thinking, and that led me quickly to the realization that good reasons need not be deductive, and to the discovery of defeasible reasoning. From there it was a short jump to a more general interest in how rational cognition works. I am interested in rational cognition in general. Epistemology is one constituent of rational cognition, practical cognition (rational decision making) another. Much of the work on rational cognition begins with the supposition that only ideal agents can be truly rational. Real agents have limited powers of reasoning and limited memory capacity. It is often supposed that such resource-bounded agents can only approximate rationality, and that as philosophers we should confine our attention to ideal agents. If one wishes, one can of course define “rationality” in this way, but this has never been what interested me. We come to philosophy wondering what we should believe, what we should do, and how we should go about deciding these matters. These are questions about ourselves, with all of our cognitive limitations. For example, it is often claimed that ideal agents, with unlimited cognitive powers, should believe all of the logical consequences of their beliefs. But we, as real resource-bounded agents, cannot do that, so that is not something we should do. What I want to know is how I, as a real agent, should go about deciding what to believe and what to do. Thus my topic is real rationality as opposed to ideal rationality. In the realm of practical decision making, I have explored this distinction at great length in my recent book (2006). Here I will focus on its implications for epistemology. For many years epistemology was derailed by the Gettier problem..