. In this chapter, induction and abduction are investigated in a nonmonotonic reasoning framework. We recall that several meanings can be given to logic-based abduction and induction. In particular, we distinguish explanatory and descriptive induction. Explanatory induction is closely related to abduction. Descriptive induction is related to abduction in a less straightforward way. While both can be modelled as deduction from a completed theory, different completion policies must be considered. Actually, induction does not require properties to be circumscribed but individuals, while abduction does not require individuals to be circumscribed but properties. 1. Introduction Both abduction and induction aim at inferring hypotheses given some observations. In the inferential perspective of Peirce, recalled by Flach and Kakas (this volume), abduction is defined as the process of coming up with a hypothesis to explain the observations. We will consider a slightly more constrained definitio...