The most basic distinction is between a thing or a substance and a property. Fess Parker, a table, and the moon are all substances. These substances have properties: Fess Parker is the world’s greatest actor, the table is stained, and so on.
A state of affairs is a substance’s having a property; that Socrates is bald is a state of affairs.
Some properties are intrinsic: the ones that things have just because of the way they are, like the property bald. Other properties are relations, like loves or is taller than.
A kind is a group or set of substances, properties, or states of affairs. Some kinds are natural: there is some reason for thinking
everything in the kind belongs together. Some philosophers think that everything in a natural kind shares the same causal powers—they can do the same things in the same conditions. (Consider
the periodic table, for instance: why is it important whether an atom is an oxygen or hydrogen atom?)
Other kinds are unnatural: they don’t share enough features, or enough of the right kind of feature, in order to qualify as a natural kind.
- List three things that form an unnatural kind.
- One of David Letterman’s best bits was a list of ‘Top 10 Rejected Oprah Themes.’ Among them was ‘Problems of Guys Named Don’. Why is this a bad idea for a talk-show theme?
On the Aristotelian picture, an essence (a.k.a. ‘species,’ ‘form,’ ‘substantial form’) has the following three features:
- it is the most fundamental explanatory property a thing possesses;
- the thing that has it cannot lose its essence and continue to exist;
- things with similar (or identical) essences form a natural kind.