Consciousness

Consciousness has three distinct meanings in the modern world. First it refers to immediate subjective experience. Second, it is the source of immediate and certain knowledge of mental states. For example, if I am in pain, I am conscious of pain and certain of this knowledge of my mental state. Third, it is self-consciousness, a concept of the self that answers the question "Who am I"?

From the seventeenth to the later part of the nineteenth century, the first two meanings of consciousness were indistinguishable and often joined by the third meaning: The presence of immediate private experience was assumed, and infallible truths about states of mind and personal or collective identities were derived from it. Since the later nineteenth century, these three ideas of consciousness have been distinguished from each other and subjected separately to criticisms and doubts.

The etymology of consciousness is derived from the Latin con (with, together) and scire (to know). When Romans shared particular knowledge, they had con-sciousness. Sharing knowledge with oneself is the etymological source of conscience. In medieval Latin, for example in the works of St. Thomas Aquinas (c. 1224–1274), consciousness came to mean a knowing subject, as distinct from an unconscious person or a plant. However, the first two modern senses of consciousness were introduced largely by René Descartes (1596–1650).