proprium one of Porphyry’s five predicables, often translated as ‘property’ or ‘attribute’; but this should not be confused with the broad modern sense in which any feature of a thing may be said to be a property of it. A proprium is a nonessential peculiarity of a species. (There are no propria of individuals or genera generalissima, although they may have other uniquely identifying features.) A proprium necessarily holds of all members of its species and of nothing else. It is not mentioned in a real definition of the species, and so is not essential to it. Yet it somehow follows from the essence or nature expressed in the real definition. The standard example is risibility (the ability to laugh) as a proprium of the species man. The real definition of ‘man’ is ‘rational animal’. There is no mention of any ability to laugh. Nevertheless anything that can laugh has both the biological apparatus to produce the sounds (and so is an animal) and also a certain wit and insight into humor (and so is rational). Conversely, any rational animal will have both the vocal chords and diaphragm required for laughing (since it is an animal, although the inference may seem too quick) and also the mental wherewithal to see the point of a joke (since it is rational). Thus any rational animal has what it takes to laugh. In short, every man is risible, and conversely, but risibility is not an essential feature of man. See also ESSEN- TIALISM , PORPHYRY , PREDICABLE. P.V.S.