Key Concepts in Descartes' Philosophy: Mind, Truth, and Reality

Descartes on Clarity and Distinction

For René Descartes, clarity and distinction are key features of evidence, signifying knowledge present to the mind. He considered knowledge genuine only if it met both characteristics:

• It is clear: Present and accessible to the attentive mind.
• It is distinct: Precise and separated from all other objects, containing only what is clear within itself.

Knowledge must possess both clarity and distinction to serve as a reliable foundation.

Descartes' Criterion of Truth

The criterion Descartes established to determine the truth of our beliefs is evidence: true propositions are those that present themselves to the intellect as clear and distinct. An approach involves the requirement or standard used for evaluating something; for Descartes, this standard was clarity and distinction.

The Cartesian Concept of Idea

Descartes used the word idea to name any content of the mind capable of representing something. While not precisely defined by Descartes, it seems to refer generically to everything in the mind, including:

• Sensations
• Objects of memory
• Objects of imagination
• Thoughts
• Emotions

Understanding Substance in Descartes

Descartes defined substance as that which requires nothing else to exist. Interpreted literally, only God (infinite substance) fits this definition, as all created things depend on God for their existence.

However, Descartes also used the term in a derivative sense to refer to created substances (finite substances), which need only God to exist:

• Thinking substance (mind, res cogitans)
• Extended substance (body, res extensa)

Substance cannot be known directly but only through its principal attribute or essential feature:

• For thinking substance: Thought
• For corporeal substance: Extension (length, width, depth)

All other properties (modes) are modifications of these fundamental attributes (e.g., imagination, sensation, and will are modes of thought; figure and motion are modes of extension).

Descartes' Definition of Thought

Descartes used the term thought (pensée, cogitatio) for everything that is within us in such a way that we are immediately conscious of it. As such, it encompasses all operations of the will, intellect, imagination, and senses.

Descartes understood this word more broadly than we typically do today; we often restrict 'thinking' to cognitive or intellectual mental acts.