Most of Freud’s contemporaries believed that the human mind was all conscious. Historians of ideas who write about the development of psychology often get Freud's original contribution wrong because they don’t attend carefully enough to what was meant by terms like “subconscious mind” and “unconscious states.”

Last month, I started a new series of essays on Freud as a philosopher. This month, I want to lay out some of the perplexing philosophical issues that Freud and his intellectual community were confronted with towards the end of the nineteenth century, and how they grappled with them.

The phrase "I think, therefore I am" or "Cogito ergo sum" might make Descartes the most-quoted philosopher of the last 400 years. But what’s the role of other people in the self? Does the self really come from one person’s solitary mind—or do the people around us inform who we refer to when we use the word “I”?

The study of philosophy, or the study of what other people have said that gets categorized under the heading 'philosophy', has the potential to leave one feeling a perpetual student. Expertise can be acquired in a so-called "field" of study. Along the way, however, students will have realized their "field" of study looks less like an actual field and more like a narrowly defined section of a bookshelf in a stuffy library. They will have also realized that one never finished studying philosophy.