Perception, thought, intentionality, and consciousness involve mental representations. We perceive and think about the world. We have impressions, images, ideas, and dreams. “Through” these we relate to the world. But what are they? Are they real things of some sort? The world itself might be out of reach, a “thing in itself” as Kant put it. What we perceive might be an illusion, as Descartes imagined. We might be in the Matrix. During the last one-hundred years, neuroscience and AI made new discoveries. But they still face old philosophical problems. Most of today’s relevant terminology in the West is derived from Ancient Greek and the Middle Ages. We are entangled in old ideas and old problems. In this course, we will dig into the roots in Plato, Aristotle, Thomas Aquinas, Descartes, and Kant; about the soul, ideas, forms, imagination, mental inexistence, intentionality, reality, and consciousness. We will read excerpts from their works and secondary literature to get an overview and gain insight.