Intelligence is a single quality, that applies to behavior: a behavior (and its subject) shows intelligence to the extent that it overcomes difficulties in ways that are novel to it, though not necessarily novel in any absolute sense. Intelligence is manifested everywhere in the world: in plants, in animals of all kinds (not necessarily mammals, or even vertebrates), in transportation systems, and in machines. In all cases, intelligent behavior is behavior that has learned useful lessons from play. The case of plants is especially interesting, because it directs our attention to an intelligence manifested not by an individual tree but by a whole forest. The case of machines received useful focus when Turing devised his test for deciding whether a machine can think. That test went counter to millennia of an anthropomorphic understanding of intelligence, evident in Aristotle (most colorfully, and unfairly, in his many disparaging comments on the octopus) and recently revived by Searle with his Chinese-room argument. In fact, Turing already anticipated Searle’s criticism by pointing out that machines had until then limited experience, and we had limited experience of them; all it takes for them to perform closer to humans is that they have as large an experience as we do.