Although problem-based learning (PBL) has become one pedagogical approach to gain currency in recent decades, its foundational underpinnings have remained obscure. This investigation seeks to elucidate the theoretical framework or assumptions upon which PBL operates. We have situated core PBL principles in the larger context of health science education, which underwent dramatic changes at the beginning of the twentieth century. The fundamental problem at that time in dental education was moving beyond a lecture-based and apprentice curriculum (students memorizing facts) to a critical thinking-based curriculum. We trace these developments and especially the principles that one thinker, who does not easily fit into any one school of thought, used to frame the problem. We found that the principles underlying the idea of PBL have existed for over a century in varying academic alleys outside of dentistry (including constructivist thought). Despite our technological advances, many of the core challenges of a century ago remain challenges today. Although PBL is certainly not the only way to provide dental students an opportunity to best develop critical thinking, it nevertheless provides an environment in which the learning process may be enhanced.