This essay analyses some remarks of Wittgenstein’s On Certainty in which Wittgenstein compares human behaviour to that of animals and says he wants to consider man as an animal. The essay’s main purpose is to show that these remarks are essentially understood as part and parcel of what Wittgenstein calls “conceptual investigations” and that, consequently, they give little support to On Certainty’s naturalistic interpretations. A second purpose of the essay is to show that Wittgenstein does not intend to combat the (...) use of “I know” in contexts such as those evoked by Moore; rather he wants to draw attention to the different ways in which we say or can say “I know.”. (shrink)