While many people think of self-knowledge as about having particular knowledge of oneself, and contemporary philosophers think of self-knowledge as about knowing one’s own mental states, historically, many thinkers have thought about self-knowledge as about knowing one’s nature. This is clear in Thomas Aquinas’s account of self-knowledge. Yet how is knowing one’s nature, which is one of the least individual aspects of oneself, self-knowledge rather than more general anthropological knowledge? This article defends the idea that there is a knowledge of one’s nature which qualifies as self-knowledge and not just anthropological knowledge. In particular, it defends Aquinas’s conception of self-knowledge in dialogue with contemporary epistemology and Leo Tolstoy’s ‘The Death of Ivan Ilyich’. It is argued that Aquinas’s account of self-cognition describes a first-personal knowledge of our nature which is self-knowledge insofar as it is acquired through reflection on one’s experience of oneself in contrast to third-personal anthropological knowledge.

The notion of immunity to error through misidentification (IEM) has played a central role in discussions of first-person thought. It seems like a way of making precise the idea of thinking about oneself ‘as subject’. Asking whether bodily first-person judgments (e.g. ‘My legs are crossed’) can be IEM is a way of asking whether one can think about oneself simultaneously as a subject and as a bodily thing. The majority view is that one cannot. I rebut that view, arguing that on all the notions of IEM that have so far been successfully defined, bodily first-person judgments can be IEM.