ABSTRACT
Models are often described as representations of target systems that are of scientific interest. Though they are seldom addressed directly, target systems are an important topic in their own right. What makes an adequate target and how to obtain it are important methodological questions in science that still need more attention from philosophers. This chapter provides an overview of the accounts of target systems developed so far with a focus on what kind of entities target systems are considered to be, if and how they should be distinguished from phenomena and models of data, and how to evaluate the task they accomplish.
