detachment, rule of See LOTTERY PARADOX, MODUS. PONEN. determinable, a general characteristic or property analogous to a genus except that while a property independent of a genus differentiates a species that falls under the genus, no such independent property differentiates a determinate that falls under the determinable. The color blue, e.g., is a determinate with respect of the determinable color: there is no property F independent of color such that a color is blue if and only if it is F. In contrast, there is a property, having equal sides, such that a rectangle is a square if and only if it has this property. Square is a properly differentiated species of the genus rectangle.
W. E. Johnson introduces the terms ‘determinate’ and ‘determinable’ in his Logic, Part I, Chapter 11. His account of this distinction does not closely resemble the current understanding sketched above. Johnson wants to explain the differences between the superficially similar ‘Red is a color’ and ‘Plato is a man’. He concludes that the latter really predicates something, humanity, of Plato; while the former does not really predicate anything of red. Color is not really a property (or adjective, as Johnson puts it). The determinates red, blue, and yellow are grouped together not because of a property they have in common but because of the ways they differ from each other. Determinates under the same determinable are related to each other (and are thus comparable) in ways in which they are not related to determinates under other determinables. Determinates belonging to different determinables, such as color and shape, are incomparable. ‘More determinate’ is often used interchangeably with ‘more specific’. Many philosophers, including Johnson, hold that the characters of things are absolutely determinate or specific. Spelling out what this claim means leads to another problem in analyzing the relation between determinate and determinable. By what principle can we exclude red and round as a determinate of red and red as a determinate of red or round?
See also JOHNSON, PROPERTY. D.H.S.