Abstract
Sayer argues that Popper defended a logicist philosophy of science. The problem with such logicism is that it creates what is termed here as a `truncated foundationalism', which restricts epistemic certainty to the logical form of scientific theories whilst having nothing to say about their substantive contents. Against this it is argued that critical realism, which Sayer advocates, produces a linguistic version of truncated foundationalism and that Popper's problem-solving philosophy, with its emphasis on developing knowledge through criticism, eschews all forms of foundationalism and is better able to account for the development of substantive knowledge claims. Key Words: critical realism fallibilism logicism post-positivism truncated foundationalism.