The notion of a thick concept was introduced by the British philosopher, Bernard Williams in the 1980s. It refers to concepts that are evaluative (like ‘right,’ ‘wrong,’ ‘good,’ ‘bad”) but also, unlike the concepts just mentioned, are descriptively rich and complex. So it draws our attention to concepts that are often set aside in contemporary philosophical discourse. Since Williams’s introduction of “thick concepts,” various philosophers have appealed to the notion in various ways. In this course, we will try to understand the possibilities and limitations of thick concepts, whether in ethics or outside of it. In the course of doing so, we might look at how that notion fits with other aspects of Williams’s philosophy.