This chapter explores philosophical issues in metaphysics. It begins by distinguishing between de re and de dicto necessity. All necessity is uniformly de re; there is simply no such thing as de dicto necessity. Indeed, in the glory days of positivism, all necessity was understood as uniformly the same: a necessary truth was always an a priori truth, while contingent truths were always a posteriori. The chapter then assesses the concept of antirealism. Antirealism is always an error theory: there is some sort of mistake or distortion or sloppiness embedded in the usual discourse. The chapter also considers paradoxes, causation, conceptual analysis, scientific mysteries, the possible worlds theory of modality, the concept of a person, the nature of existence, and logic and propositions.