Since the first use of "scientific literacy" in the late 1950s, numerous science educators and policy makers have reconceptualised the term to such an extent that it has been described as being "ill-defined and diffuse". Despite this lack of clarity, the term is the focus of curriculum standards in many countries and is at the heart of international comparisons of student attainment including the Organisation for Economic Cooperation and Development's (OECD) Programme for International Student Assessment (PISA) study. Uncritical use of the term masks the existence of deep-seated philosophical clashes that hinder reform of science education in many countries throughout the world.