Accidental property

An accident, in philosophy, is an attribute that may or may not belong to a subject, without affecting its essence.

Aristotle made a distinction between the essential and accidental properties of a thing. Thomas Aquinas and other Catholic theologians have employed the Aristotelian concepts of substance and accident in articulating the theology of the Eucharist, particularly the transubstantiation of bread and wine into body and blood.

In modern philosophy, an accident (or accidental property) is the union of two concepts: property and contingency. Non-essentialism argues that every property is an accident. Modal necessitarianism argues that all properties are essential and no property is an accident.

Aristotle made a distinction between the essential and accidental properties of a thing. For example, a chair can be made of wood or metal, but this is accidental to its being a chair: that is, it is still a chair regardless of the material from which it is made. To put this in technical terms, an accident is a property which has no necessary connection to the essence of the thing being described.

To take another example, all bachelors are unmarried: this is a necessary or essential property of what it means to be a bachelor. A particular bachelor may have brown hair, but this would be a property particular to that individual, and with respect to his bachelorhood it would be an accidental property. And this distinction is independent of experimental verification: even if for some reason all the unmarried men with non-brown hair were killed, and every single existent bachelor had brown hair, the property of having brown hair would still be accidental, since it would still be logically possible for a bachelor to have hair of another color.

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