 Kant saw as one of the functions of philosophy to determine the precise unifying scope and value of each science. For Kant, the unity of science is not the reflection of a unity found in nature, or, even less, assumed in a real world behind the apparent phenomena. Rather, it has its foundations in the unifying a priori character or function of concepts, principles and of Reason itself. Nature is precisely our experience of the world under the universal laws that include some such concepts. And science, as a system of knowledge, is “a whole of cognition ordered according to principles”, and the principles on which proper science is grounded are a priori (Preface to Metaphysical Foundations of Natural Science). A devoted but not exclusive follower of Newton’s achievements and insights, he maintained through most of his life that mathematization and a priori universal laws given by the understanding of it were preconditions for genuine scientific character (like Galileo and Descartes earlier, and Carnap later, Kant believed that mathematical exactness constituted the main condition for the possibility of objectivity). Here Kant emphasized the role of mathematics coordinating a priori cognition and its determined objects of experience. Thus, he contrasted the methods employed by the chemist, a “systematic art” organized by empirical regularities, with those employed by the mathematician or physicist, which were organized by a priori laws, and held that biology is not reducible to mechanics—as the former involves explanations in terms of final causes—(see Critique of Pure Reason, Critique of Judgment and Metaphysical Foundations of Natural Science). With regards to biology—insufficiently grounded in the fundamental forces of matter—its inclusion requires the introduction of the idea of purposiveness (McLaughlin 1991). More generally, for Kant unity was a regulative principle of reason, namely, an ideal guiding the process of inquiry toward a complete empirical science with its empirical concepts and principles grounded in the so-called concepts and principles of the understanding that constitute and objectify empirical phenomena (on systematicity as a distinctive aspect of this ideal and on its origin in reason, see Kitcher 1986 and Hoyningen-Huene 2013).