At the outset, Hamlet remarks on the futility of attempting to guess at his state of mind by appeal to the notatio, or standard behavioral model, favored by the science of physiognomy. Although the possibility of knowing other minds is provided for by Renaissance theory of natural law and by certain tenets of Neoplatonism, Hamlet's initial skepticism is in full accord with the weight of received opinion—e.g., with folk wisdom, orthodox theological authority, and traditional reservations about friendship and selfknowledge. The deceptiveness of notatio, moreover, is illustrated in the play by the hubris of Polonius' art of espionage and by the bitter testimony of Claudius to his success as a dissembler. In practice, however, both Claudius and Hamlet rely with no less confidence than Polonius on the possibility of reading the inner by the outer man. Though Hamlet is sustained in this confidence by a hopeful theory of histrionic performance, a scholar's habits of observation, a flair for satirical portraiture, and even a few trivial successes, the treachery of notatio is ominously revealed, along with the Polonian arrogance of relying on it, in his encounter with Gertrude, and especially in his conception of how the “Mousetrap” can be sprung.