In Francis Bacon, we find, as in the whole Renaissance, the ideal of the regnum hominis, of the rational domination of nature, which is the purpose of knowledge and also of the practical organization of knowledge. Bacon offers an encyclopedia of the different forms of knowledge, an organic arrangement of the different sciences. We have a philosophy understood as rational knowledge and including various disciplines, and philosophy in the strictest sense or first philosophy, including the more general notions, i.e. the valid axioms for different sciences.
Modern philosophy, therefore, develops in close connection with the sciences, to which its relationship is dual: on the one hand, philosophy wants to imitate their methodical rigor and, from this point of view, to become a science itself; on the other hand, it claims to have its own specific field of investigation that establishes the foundations of sciences. R. Descartes says that it is ‘first’ philosophy, dedicated to more general notions. From this the image of knowledge as that of a tree, « the roots of which are the metaphysics, the trunk is physics, and the branches rising from this trunk are all the sciences».
T. Hobbes, B. Spinoza, G.W. Leibniz conceive philosophy according to an analogous rationalistic scheme, i.e. as the science that studies the ultimate reasons for phenomena, using a rigorous method borrowed from mathematics. But while in Leibniz there is a theological recovery, in Hobbes and Spinoza we find a clear separation of philosophy and theology, because theology concerns notions not subject to rational analysis and because its object is faith, whose purpose is obedience and piety, and not the truth, which is the only purpose of philosophy.
With J. Locke philosophy takes as its essential task the examination of the validity and the limits of knowledge, thus becoming a critical philosophy. Before proceeding to the construction of metaphysical buildings it is necessary to analyze our ability to know. The result of the investigation is that experience is the foundation and origin of all our knowledge, and thus the methodical basis of philosophy.