accessibility between two worlds See POSSIBLE. WORLD. accident, a feature or property of a substance (e.g., an organism or an artifact) without which the substance could still exist. According to a common essentialist view of persons, Socrates’ size, color, and integrity are among his accidents, while his humanity is not. For Descartes, thinking is the essence of the soul, while any particular thought a soul entertains is an accident. According to a common theology, God has no accidents, since all truths about him flow by necessity from his nature. These examples suggest the diversity of traditional uses of the notion of accident. There is no uniform conception; but the Cartesian view, according to which the accidents are modes of (ways of specifying) the essence of a substance, is representative. An important ambiguity concerns the identity of accidents: if Plato and Aristotle have the same weight, is that weight one accident (say, the property of weighing precisely 70 kilograms) or two (one accident for Plato, one for Aristotle)? Different theorists give different answers (and some have changed their minds). Issues about accidents have become peripheral in this century because of the decline of traditional concerns about substance. But the more general questions about necessity and contingency are very much alive. See also CONTINGENT , ESSENTIALISM , PROPERT. S.J.W.