Pragmatic theories of truth are best understood in the light of Charles S. Peirce's declaration: "...there is no distinction of meaning so fine as to consist in anything but a possible difference of practice". The above quote represents the claim that when one knows how an object will react to experimental handling, one has achieved a clear idea of that object. To say that a substance is hard is to say that it will not be scratched by other substances.

Peirce's criterion of meaning was pointed against traditional Cartesian subjectivism. As Peirce saw it, Descartes took an idea to be clear if it seemed clear to him, never considering the possibility that an idea may seem clear without really being clear. It is not surprising, therefore, that Peirce, in considering the meaning of truth, insisted on its public character, deploring the Cartesian view, according to which the individual judgement is the test of truth. He argued that metaphysical visions of truth and falsity that envisage them as something existing apart from the conduct of inquiry is wrong. Moreover, the doubt that impels scientific investigation is real, but its philosophical counterpart, Cartesian doubt, is an illusion.

Peirce's definition was an attempt to clarify truth as it shows up in the practice of inquiry. By defining truth as 'absolute fixity' of beliefe, Peirce set it apart from the fixed opinion of the scientific community, which is all that inquiry yields.

Peirce rejects Certecianism and opts for experimentalism which has three characteristics: 1. Denial of the idea that philosophy must begin with universal doubt; 2. The spirit of experimentalism denies that the ultimate test of certainty is to be found in the individual consciousnss; 3. Denial of the idea that a philosophical theory should be a single thread of inference, in the manner of Descartes.