Phil 21 Supplemental Notes on the Essential-Accidental Property Distinction
The essential properties of an individual thing are the set of properties that it must have to be a thing of a given kind. All trees, for example, must share certain essential properties in common to be classified as trees. Likewise for people, cats, planets or amoebas. Our ability to recognize a particular thing as a thing of a given kind rests on our knowledge of its essential properties. In the lingo of philosophy the accidental or non-essential properties of a thing are the innumerable other properties it has or may have at a certain point in time, which may include features of its appearance, location, pattern of movement, relations to other things, origin and so on.
Why is this a philosophical concern? Don’t dictionary definitions of general terms tell us the essential properties of the things the word stands for? For the most part, yes, but dictionaries have their limits. How to classify a given kind of thing is sometimes a matter of great dispute. The recent controversy among astronomers over whether to still classify Pluto as a planet is a case in point. A dictionary cannot settle this matter; we leave it up to the astronomers to decide. Similarly, many controversies in philosophy involve disagreements over the essential properties of a given kind of thing. What is essentail to being a person? a mind? a morally right action? a democratic society? It takes a convincing argument to settle these disputes and convincing arguments can sometimes be hard to come by.
Contemporary philosophers approach the problem of essential properties
somewhat differently from those in Locke’s day.
Locke understands essential properties to be the necessary and
sufficient conditions for a thing to be of a given kind. In the abstract, anything of kind K must
have, say, properties A,B,C and D as individually
necessary and jointly sufficient conditions.
A closer look, however, at the way we classify things in practice
reveals a complication. We don’t
necessarily require that every K have all of the properties A through D. Perhaps the great majority of Ks do, but some
Ks may have only A,B and C, while others have A, C and
D and so on. Our concept of a given kind
of thing can have fuzzy boundaries. Not
surprisingly, there can be significant disagreements over the proper
classification of things that lie on the boundaries of our concepts. Take, for example, the concept of a
person. We traditionally have required,
at a minimum, that anything that is to count as a person must at least have a
human body and a rational mind. What
then should we do about someone who has fallen into a permanent coma or
advanced altzheimers and no longer has a rational
mind? Reasonable people can differ over the
best answer to this question and