An exploration of the details of counterpart theory, and some applications of the view. In Chapter 1, I set out the view and clarify the most important features: that the counterpart relation is a context dependent similarity relation, and that individuals are world-bound entities. I then set out what I take to be the most promising methods of filling in important details. Chapter 2 is a discussion of an alternative view, lump theory. I attempt to distinguish lump theory from counterpart (...) theory, and argue that several attempt to do so fail. Chapter 3 is an attempt to apply counterpart theory for individuals to properties. I attempt to stay as close to the standard view as possible, but find it necessary to modify the world-bound condition. I suggest a version of property counterpart theory that overcomes the obstacles I have identified. The final chapter is a discussion of a recent attempt to apply counterpart theory to the comparativist view of quantitative properties. I argue that an attempt to rely on counterpart theory to overcome an objection is unsuccessful. (shrink)