Some of our philosophical problems with concepts are the result of their history, claims Ian Hacking. In one sentence, he encapsulates what his project of historical ontology entails: it is an investigation of concepts in the sense of Cambridge language analysis and at the same time a history of philosophy and science. For this project, Hacking also draws on some insights from Michel Foucault. In this way, he connects Foucault's archaeology of knowledge with Wittgenstein's therapy of language confusions. He makes it clear that many of our beliefs depend on the styles of rationality in which they are justified. Hacking, similar to Nelson Goodman, dismisses the idea of a single eternal truth in his non-subjectivist nominalism and relativism. Thus, he avoids the implausibilities of social constructivism.