Graham Priest

deductively valid inference is one for which there is no situation in which all the premisses are true, but the conclusion is not.

But there are good reasons to suppose that ‘or’ and ‘and’, as they occur in English, are not truth functions – at least, not always.

Again, it is not merely the truth values of the disjuncts that are important, but the existence of a connection of a certain kind between them.

Thus, it is not just the truth values of the conjuncts that are important, but which conjunct caused which.

In a situation, a unique truth value (T or F) is assigned to each relevant sentence.

A situation comes furnished with a stock of objects.

(Compare: Everyone has a mother; it does not follow that there is someone who is the mother of everyone.)

The sentence nP is true in a situation if the object referred to by n has the property expressed by P in that situation.

definite descriptions, or sometimes just descriptions

descriptions have the form: the thing satisfying such and such a condition.