Descartes Versus Empiricism: Rationalism and Experience

The father of rationalism, Descartes, can be compared to philosophical empiricism, which posits experience as the sole basis of human knowledge. This idea was born in Britain and developed during the 17th and 18th centuries. Closely related to the Enlightenment, it influenced subsequent philosophies, particularly those rooted in the principles of political liberalism.

John Locke: Challenging Innate Ideas

The first major empiricist was Locke, the founder of the theory of knowledge. His starting point contrasts with Descartes' philosophy, which is based on mathematical rigor. Locke's main criticism of Descartes is the affirmation of innate ideas. To demonstrate this, he offers several arguments:

• Neither the mad nor children possess these fundamental truths.
• If these ideas were innate, they should be universally known without exception.
• It is possible to have an idea without consciously knowing it.
• Locke intended to be more extreme, applying doubt even to innate ideas—something Descartes did not fully do, despite it being central to his method.

David Hume: Radical Empiricism and Causality

Hume is more radical than Locke, taking empiricism to its ultimate consequences and contradicting the principle of causality. Hume argues that this principle is worthless because it is not a rigorous scientific principle; it is based merely on:

1. Continuity in time between two events.
2. Continuity in space between cause and effect.
3. Regularity in the effect of the two preceding conditions.

Locke argued that the existence of God is necessary as our cause, but Hume rejected this, stating that we only know impressions. We have no impressions of causes, so the existence of God is not provable by rational arguments. Hume does not support the existence of the cogito, which is central to Cartesian philosophy concerning the three substances (res cogitans, res extensa, and God).

Perceptions: Impressions vs. Ideas

Hume defined sensory perceptions as impressions, and ideas as the faint copies or footprints of impressions. In contrast, Descartes classified ideas only as adventitious, fictitious, or innate.

Knowledge Types

From his classification of perceptions (impressions and ideas), Hume derived possible types of knowledge:

• Knowledge of facts (based on impressions).
• Relationships between ideas, which give rise to universal and necessary knowledge.

Metaphysics

For Descartes, metaphysics exists, as he views it as the unique, vital, and true scientific knowledge, whereas Hume's framework severely limits its scope.