Abstract
Russell maintained that a person can have knowledge about a particular only if he is acquainted with some particular. In a similar vein, Chisholm has argued that a person cannot identify a particular unless he identifies some particular per se. According to Chisholm, a person identifies a particular per se just in casehe has knowledge of its haecceity or individml essence. Chisholni urges us to accept the following controversial claim concerning haecceities: none of us has knowledge of the haecceity of a particular physical object or person, x, when he perceives x by means of his senses, and picks x out as that thing. However, Chisholm does not offer a compelling argument to support this claim. In this paper I aim to show that Chisholm's claim is fundamentally correct.