The empiricist claim is easy to state and surprisingly demanding to hold. Nothing gets into the mind except through experience — so any concept you possess must be traceable back to something you encountered, and any belief must ultimately answer to observation. It sounds like modest common sense. Hume showed it is not.
Locke set the programme by attacking innate ideas. If certain principles were stamped on the mind at birth, they should be present in everyone — yet children, and people from cultures without the relevant traditions, plainly lack them. He concluded that the mind starts as white paper, and that all our materials come from two sources: sensation, our experience of external objects, and reflection, our observation of our own mental operations. Everything else is built by combining, comparing and abstracting from those.
Berkeley applied the principle more consistently than Locke and reached a startling place. Locke had retained material substance as the unperceived support of qualities. But if all ideas derive from experience, Berkeley asked, where did the idea of an unperceivable substratum come from? Nowhere — so it is not merely unproven but meaningless, and what exists is minds and their ideas. Empiricism, rigorously applied, had produced idealism.
Hume went furthest. His test is that every genuine idea must be traceable to an impression. Apply it to causation: you observe the cue ball strike the red, and the red move. You observe succession and constant conjunction. You never observe the necessary connection that makes it a case of causing rather than merely following — so the idea of necessity comes not from the world but from a habit of expectation formed by repetition. Apply the test to the self: look inward and you find perceptions, never a perceiver having them. And apply it to induction and no non-circular justification appears. Empiricism's own method dissolves three things it seemed obvious we knew.
Later formsThe twentieth century.
Logical positivism revived empiricism in a hard form: a statement is meaningful only if it can be verified by observation or is true by definition. This was intended to eliminate metaphysics as literal nonsense, and it failed for a reason worth remembering — the verification principle is neither verifiable by observation nor true by definition, so by its own standard it is meaningless. Quine then attacked the underlying picture from another direction, arguing that individual statements cannot be tested against experience one at a time; theories face the tribunal of experience as wholes, so any statement can be retained if we adjust elsewhere.
ObjectionsWhere it strains.
Mathematics and logic. These do not appear to be learned from observation, and no amount of counting establishes that arithmetic could not be otherwise. Strict empiricists must treat them as true by definition, which many find an unsatisfying account of why they apply so well to the world.
Theory-ladenness. Observation itself turns out not to be a neutral foundation — what counts as data depends on the framework you bring. That complicates any picture in which experience is the bedrock everything rests on.
Innate structure. Empirical work in linguistics and cognitive science suggests the mind is not a blank slate but arrives with substantial built-in structure — which is an interesting reversal, since it is evidence against empiricism produced by empirical methods.