Rationalism holds that reason can provide substantive knowledge independently of sensory experience, whereas empiricism holds that knowledge of the world originates primarily, or entirely, through sensory experience.
The Reasoning
Rationalists argue that some truths can be known a priori, meaning independently of particular experiences. Logical and mathematical truths are standard examples: their justification appears to depend on rational insight or deduction rather than observation. René Descartes also used systematic doubt and the proposition “I think, therefore I am” to establish certainty through reason.
Some rationalists defend innate ideas or principles possessed by the mind rather than acquired through experience. They may argue that sensory information is unreliable and cannot by itself establish universal or necessary truths.
Empiricists argue that substantive knowledge is a posteriori, meaning justified through experience. John Locke described the mind at birth as a tabula rasa, or blank slate, and claimed that ideas arise from sensation and reflection. David Hume distinguished between immediate impressions and the less vivid ideas derived from them.
| Issue | Rationalism | Empiricism |
|---|---|---|
| Primary source of knowledge | Reason | Sensory experience |
| Characteristic justification | A priori reasoning | A posteriori evidence |
| Typical method | Deduction from rational principles | Observation and induction |
| Associated philosophers | Descartes, Leibniz and Spinoza | Locke, Berkeley and Hume |
| Main difficulty | Explaining how reason alone reveals reality | Justifying universal claims from limited experience |
A common misconception is that rationalists reject experience and empiricists reject reason. Both normally use reason and experience; the disagreement concerns which source is foundational and whether reason can generate substantive knowledge independently of experience.
Exam Technique
In an IB Philosophy response, define both positions precisely, explain the a priori/a posteriori distinction, and use philosophers to develop arguments rather than merely naming them. For evaluation, test whether rationalism can justify innate knowledge and whether empiricism can overcome problems such as unreliable perception and the problem of induction.
