 The properties listed in (6) can very naturally be called ‘kinds of necessity,’ and in some contexts they are the properties expressed by necessity operators like ‘must’ and ‘could not have been otherwise.’ But that is not true of every property that can be defined from some kind of necessity by relativization or restriction. For example, we can define a property by relativizing metaphysical necessity to the class of truths stated in a certain book, but it would not be natural at all to call this property a kind of necessity. It is not plausible that there is a special form of necessity that attaches to all and only the propositions necessitated by the truths in the book. Similarly, the property defined by restricting metaphysical necessity to the truths about cheddar cheese cannot naturally be called a kind of necessity. There is no form of necessity that applies to just those necessary propositions that deal with cheddar and to none of the others. It is a good question what distinguishes those properties defined by relativization and restriction that we are willing to count as forms of necessity from the rest. Perhaps the most natural answer is that the distinction is dictated by our interests and concerns, and does not reflect a deep metaphysical difference.