Experience for Mill is that which can be checked, tested, and proven by careful observation and analysis. Experience must be used to test the inferences we make from experience. Mill observes that the fundamental laws of mathematics and logic, which the supporters of intuitive knowledge had long pointed to as proof that there are some things we know that require no experience, are in fact no more than generalizations from experience. He argues that the law of contradiction, another supposedly innate idea which holds that nothing can be both true and not true, is purely a summary of the inherent incongruity of belief and nonbelief.

Mill maintains that any accuracy of knowledge is only hypothetical, and thus fictitious. He views the law of causation (the fact that every event has a cause) as very important to his inductive system, as a generalization from the experience of an invariable and unconditional sequence. Further, Mill acknowledges only one kind of inference—that which occurs from particulars to particulars—and he uses inference to interpret the record of particular experiences, since they alone provide evidence on which any kind of conclusion can rest.

Popular pages: Selected Works of John Stuart Mill