Impartial observers from other planets would consider ours an utterly bizarre enclave if it were populated by birds, defined as flying animals, that nevertheless rarely or never actually flew. They would also be perplexed if they encountered in our seas, lakes, rivers, and ponds, creatures defined as swimmers that never did any swimming. But they would be even more surprised to encounter a species defined as a thinking animal if, in fact, the creature very rarely indulged in actual thinking.