The title of a new paper by Russ Abbott of California State University caught my eye today: If a tree casts a shadow is it telling time? (PDF format). The title is an update to the classic philosphical question; if a tree falls in a forest with no one around to hear it, does it make a sound? The point the author is getting at is that natural processes are only computational if they are used to externalize the thoughts of someone (or something) that's conscious. He starts with questions we intuitively know the answer to. Can a word processor "have an idea"? Can Google's GMail service "read your email"? From there, the paper goes on to talk about all sorts of computational machines ranging from a 13th century symbol manipulator to Turing machines and artificial intelligence.