compare and evaluate rationalism and empiricism as accounts of the source of knowledge, with reference to Descartes, Locke, Hume and Kant

What this dot point is asking

QCAA wants you to compare the two great rival accounts of where knowledge comes from: rationalism (reason) and empiricism (experience). You need the central claims, the leading figures (Descartes, Leibniz; Locke, Berkeley, Hume), the key distinctions (a priori versus a posteriori; analytic versus synthetic), and Kant's attempt to combine them. This is core epistemology that links to scepticism and the theory of knowledge.

The answer

The dispute

The debate concerns the source and justification of knowledge. Rationalists hold that significant knowledge can be gained by reason independently of sense experience, and often that we have innate ideas. Empiricists hold that all substantive knowledge derives ultimately from experience, and deny innate ideas. Two distinctions frame the debate:

• A priori (knowable independently of experience, such as mathematics) versus a posteriori (knowable only through experience).
• Analytic (true by meaning, such as "all bachelors are unmarried") versus synthetic (true in virtue of the world).

Rationalism

Rene Descartes sought certainty through reason. Doubting all he could, he reached the indubitable "I think, therefore I am," then argued from reason to the existence of God and the external world. He held some ideas are innate, implanted in the mind, not derived from the senses (such as the idea of God, or of a perfect triangle). Gottfried Leibniz argued that the senses give particular instances but only reason yields necessary truths (mathematics, logic), which experience could never establish, since experience shows only what is, not what must be. Strength: it explains our knowledge of necessary, universal truths. Objection: innate ideas are hard to establish, and pure reason alone seems unable to deliver substantive knowledge of the world.

Empiricism

John Locke argued the mind is at birth a tabula rasa (blank slate); all ideas come from experience, whether sensation (outer) or reflection (inner). There are no innate ideas. David Hume sharpened this: every idea is a faint copy of a prior impression (a sense experience or feeling); a term with no corresponding impression is empty. Hume used this to attack metaphysical notions and to expose the problem of induction and the weakness of our idea of causation (we observe constant conjunction, not a necessary connection). Strength: empiricism ties knowledge to evidence and fits scientific method. Objection: it struggles to account for necessary truths and universal laws, and Hume's own scepticism about causation and induction shows how far strict empiricism can corrode ordinary knowledge.

Kant's synthesis

Immanuel Kant argued, in the Critique of Pure Reason (1781), that both camps were half right. Knowledge requires both sensory input and the mind's own organising structures (the forms of space and time and the categories such as causation). His famous line: thoughts without content are empty, intuitions without concepts are blind. Crucially he argued for synthetic a priori knowledge: substantive truths (such as that every event has a cause, or the truths of geometry) that are known independently of particular experience yet are not merely analytic. Mathematics and the framework of science fall here. Kant thus rejects both pure rationalism and pure empiricism.

Try this

Q1. Distinguish rationalism from empiricism. [3 marks]

• Cue. Rationalism: reason gives substantive knowledge independent of experience, often innate ideas; empiricism: all ideas derive from experience.

Q2. Explain Hume's claim that ideas are copies of impressions. [3 marks]

• Cue. Every idea is a faint copy of a prior sense impression; a term with no impression is empty.

Q3. Explain what Kant meant by synthetic a priori knowledge. [4 marks]

• Cue. Substantive (not true merely by meaning) yet knowable independently of particular experience, such as that every event has a cause.