This book is a collection of my essays, dating from 1969, concerning the metaphysics of modality. The first two chapters are a defense of the idea of modality de re against criticisms from William Kneale and W.V. Quine, and an elaboration on the notions of possible worlds and essences. In the third chapter, I conclude that the Theory of Worldbound Individuals is false, even when fortified with Counterpart Theory. Chapter 4 contains an argument for the conclusion that there neither are, nor could have been, possible but nonexistent objects. In the next chapter, I develop this theme in greater detail and argue for the compatibility of actualism -- i.e., the view that there neither are, nor could have been, any nonexistent objects --and possible worlds. Both Chs. 6 and 7 contain an account of the relationship between proper names and essences, my view being that proper names express essences and that sometimes different proper names for the same object express different essences of that object. The end of Ch. 7 and all of Ch. 8 are an examination of existentialism (the theory that propositions and states of affairs ontologically depend on their subjects) and arguments against it. In Ch. 9, I defend my theory of modality against objections raised by John Pollock. In Ch. 10, I sketch out what the commitments of modal realism are, and argue that David Lewis's modal theory is not a modal realist theory. Finally, in the concluding chapter I argue that propositions cannot be concrete objects.