The aim of this article is to interpret the naturalist epistemological project of W. Quine from a problematic nucleus that we can identify in I. Kant, especially in the Critique of Pure Reason, which is expressed in the categories of explanation-justification, experimental psychology and transcendental philosophy. The hypothesis of our work is that the naturalization of epistemology in a psychology by Quine is possible due to a dissolution of the limits of the concepts of explanation and justification, which have in Quine a translation in the notions of concept and doctrine. To account for this, (i) we will propose, in a general way, the Kantian problematic nucleus about the distinction between explanation and justification and its relationship with the experimental psychology of the 18th century; ii) we will analyze some important texts of W. Quine where he bases the project of a naturalization of epistemology. Our focus will be to establish the relationship between concept and doctrine as translations of Quine of the concepts of explanation and justification; (iii) finally; we will describe the psychology as a new epistemology and observational statements as an expression of this epistemological turn of Quine.