Predicate P(x, y) (x is the parent of y). Consider the premise: If one person is the child of a second, then the second is not the child of the first. Conclude from this premise that no person is his own child. Provide a proof of this argument.

The following problem deals with the fourteenth-century nominalistic philosopher William of Ockham and the great seventeenth-century philosopher Thomas Hobbes. Provide a proof for the following argument: None of Ockhams followers like any realist. Any of Ockhams followers likes at least one of Hobbes followers. Moreover, Ockham has followers. Therefore, some of Hobbes followers are not realists.