While very popular in public discourse about education, critical thinking education is still a work in progress. Two key conditions for successfully addressing critical thinking education are lacking: (a) the availability of a clear, specific, and operational definition, and (b) a deeper understanding of the natural cognitive bases of critical thinking. We, therefore, propose a theoretical framework for critical thinking education, grounded on a cognitive approach. Starting from a restrictive characterization of critical thinking--defined as the capacity of evaluating the epistemic quality of information, and of calibrating one's confidence in relationship to it--we identify specific mechanisms subserving critical thinking that are present in early human development. We refer to these mechanisms as the natural building blocks of critical thinking. On this naturalistic ground, effective educational strategies can be envisaged that both harness the natural building blocks of critical thinking and help overcome its shortcomings.