In this and the next several assignments, Kripke extends the ideas developed in his account of identities between proper names to terms for properties and kinds. He first focuses on the essential properties of an individual.

There are immediate connections between this discussion and things you’ve already seen. First, an ascription of an essential property is a claim of necessity de re. In each case, it claimed about a thing that something is necessarily true of it. Second, one example of an essential property is the property of being Aristotle, or being Phosphorus—i.e., the property expressed by ‘is N’, where N is a proper name. Kripke’s main point in these pages then generalizes his claim about identities between proper names: other ascriptions of essential properties also might be known only a posteriori even though they are necessary.

He makes this point with regard to two examples, first Queen Elizabeth (pp. 110-113) and then a wooden table (pp. 113-115), with his main discussion of the latter appearing in several long footnotes. In each case, he will point to an idea that appeared several times in his discussion of identities between names (see especially p. 104): something that seems consistent with what we know may really be impossible and, when we seem to conceive its possibility, we are imagining a situation that is “qualitatively identical” to the actual one but in fact involves different objects.