In philosophy, supervenience refers to a relation between sets of properties or sets of facts. X is said to supervene on Y if and only if some difference in Y is necessary for any difference in X to be possible. Some examples include: Whether there is a table in the living room supervenes on the positions of molecules in the living room. The truth value of (A) supervenes on the truth value of (¬A). For the same reason, the truth value of (¬A) supervenes on that of (A). Properties of individual molecules supervene on the properties of individual atoms. One's moral character supervenes on one's action(s).These are examples of supervenience because in each case the truth values of some propositions cannot vary unless the truth values of some other propositions vary. Supervenience is of interest to philosophers because it differs from other nearby relations, for example entailment. Some philosophers believe it possible for some A to supervene on some B without being entailed by B. In such cases it may seem puzzling why A should supervene on B and equivalently why changes in A should require changes in B. Two important...