This is a question that the ancients asked, and one that crops up a few times in 20th century philosophical discussions. When it is mentioned, it is usually as an example of a problem that looks to be both deep and in principle insoluble. Unsurprisingly, then, it seems to have fallen by the scientific, cosmological and philosophical waysides. But sometimes I wonder whether it really is insoluble (or senseless), or whether science may one day surprise us by finding an answer.
ANDY CLARK is Professor of Philosophy and Cognitive Science at the University of Sussex, UK. He was previously Director of the Philosophy/Neuroscience/Psychology Program at Washington University in St. Louis. He is the author of Microcognition: Philosophy, Cognitive Science and Parallel Distributed Processing, Associative Engines, and Being There: Putting Brain, Body and World Together Again.