Abstract

The following dissertation explains the psychologism debate as it played out in the 19thand early 20th Centuries and then shows how Martin Heidegger radicalized the debate by undermining its key themes and assumptions. First, I explain each side of the psychologism debate, starting with the psychologicists. I explore the philosophies of Jakob Friedrich Fries and John Stuart Mill in order to encapsulate the full spectrum of psychologism in the 19th Century, from Neo-Kantian to British Empiricist. The investigation will show a set of common themes within psychologism, such as the grounding of logic in the constitution of the human subject, a reliance on introspection, and the prioritization of epistemology over metaphysics. I then turn to the logicists, focusing on Gottlob Frege and Edmund Husserl. I start by explaining two influential arguments against psychologism: that it treats logical objects as mental entities and that it devolves into relativism. I analyze how both Frege and Husserl developed alternate explanations for the foundations of logic, where Frege grounded logic in the relationships of objects in an ideal third realm and Husserl founded them on the relationships between the ideal objects of intentional experience. I end the section with a brief explanation of logicism’s relationship to the themes highlighted in the prior part, namely that logicism founded logic on the object side of the subject-object dichotomy but agreed with the prioritization of epistemology. The final part of the dissertation will be Heidegger’s critique and radicalization of the psychologism debate and his own understanding of logic. It starts with his critique of Husserl, v followed by a Heideggerian critique of Frege, and finally his critique of psychologism. I show that Heidegger undermined the debate by arguing that theoretical modes of engagement with the world were derivative of our more fundamental ontological structure, that the subject-object dichotomy is illegitimate, and that the psychologism debate relies on a flawed understanding of truth. Afterward, I explain Heidegger’s philosophy and construct a Heideggerian understanding of logic based on his understanding of truth and the logos.