The aim of this seminar is to explore Aristotle´s theory of thinking (noein) and reason (nous) as developed primarily in DA III.4-5. In three units, we will ask how Aristotle defines (1) the objects of thought (the essential feautures of reality), (2) the activity of thinking (a very specific kind of "being affected"), and (3) the capacity for thinking, i.e. the reason itself.