Scientific rationality evolved branching in different conflictual directions. This chapter focuses on the coevolution of Empiricism and Rationalism from the late Renaissance through the Enlightenment. This process framed the Scientific Revolution as a shift in worldview characterized by growing individualism, the consequent vindication of freedom of thought, systematic mathematization of science, and an increasing link between science and technology. Leonardo was an emblematic precursor of this new synthesis, embodying the fusion of art, philosophy, science, and technology. The revival of the heliocentric hypothesis by Copernicus, rooted in Pythagorean thought, and its refinement by Kepler using Tycho Brahe’s improved empirical data are presented as key steps. Bacon’s foundations of Empiricism, emphasized the crucial role of induction from empirical evidence. He also warned against ‘idols’ distorting the mind. Galileo and Huygens further advanced the mathematization of science, integrating systematic experimentation with mathematics and technology. Newton’s Principia represents a culmination of this evolutionary process, unifying celestial and terrestrial mechanics through universal gravitation. The resurgence of Rationalism, led by Descartes’s analytic geometry, and Leibniz’s emphasis on logic and innate intellectual structures, provided a constructive counterpoint to Empiricism. Finally, Hume’s radical Empiricism, criticizing induction and causality, exposed the limits of both traditions, paving the way for the Kantian synthesis.

Chapter 1 traces the conceptual history of judgments of perfection from Leibniz and Wolff to Kant, clarifying their significance for art criticism. In rationalist aesthetics, perfection was identified with beauty, and judgments of perfection were considered aesthetic judgments governed by rules. Kant’s rejection of this view marked a decisive break with the rationalist tradition, but his transformation of the concept has been largely overlooked. This chapter reconstructs Kant’s reinterpretation: judgments of perfection become nonaesthetic evaluations that attribute goodness to an object relative to a concept of its kind, such as “Blade Runner is an excellent neo-noir film.” These judgments remain important within Kant’s framework, not as substitutes for judgments of taste but as judgments that can inform and support aesthetic evaluation. By recovering this neglected role, the chapter lays the groundwork for a Kantian account of criticism that honors Kant’s rejection of aesthetic testimony and general principles of taste while making room for reasoned evaluation.

This chapter focuses on the relationality that constitutes the Romantic Self, highlighting the ethical and political consequences that derive from it. The Romantics refuse the lexicon proper to modern political thought, centred on the concept of sovereignty and autonomy: they highlight the illusory essence of these concepts and the dangers they imply. Consistently, they also dismantle the possibility to write a political theory that pretends to offer universal principles. Relations are not extrinsic elements added to a fully formed subject and to be considered only after the identity of the subject has been defined. Relations are what we are. That is why in its political reflections, Romanticism’s primary polemical target is modern contractualism, founded on the tacit assumption that it is possible to study human beings in their individuality, skating over the interplay among them. This chapter shows how the idea of forces and the priority given to relationships influence the Romantic political concepts. These concepts in particular will be scrutinised: representative, constituent and constituted powers, democracy, individuality, equality, and justice.

Kant states that empirical concepts, unlike pure concepts, are drawn from experience. Commentators are divided on whether this commits him to empiricism. I develop a rationalist reading that ascribes to Kant an epigenetic account of empirical concepts. To pave the way for this account, I first discuss Leibniz’s innatist alternative and then examine the parallel between Kant’s arguments about the origin of categories (pure concepts) and about biological formations. In both arguments, Kant defends a model of epigenesis that postulates an innate ‘preformation’ (in the form of ‘germs’ and predispositions) in the relevant cognitive faculty or organic species, while leaving room for external material conditions to play an indispensable role. The same model, I argue, can be extended to the formation of empirical concepts. I then connect this Kantian model with recent literature in cognitive science on the ‘epigenesis of mind’ and with the ongoing controversy over concept empiricism.

I draw a contrast between what I call a ‘presentational-phenomenological model of apprehension and ultimate evidence’ – which I attribute to Descartes, Locke and Hume – and Leibniz’s ‘logical-conceptual model of apprehension and ultimate evidence’. Although there are different uses of the word ‘concept’, Leibniz’s model, in my view, illustrates the strictest and best notion of the concept of concepts: one that centrally relies on logic.

Corey Dyck discusses the eighteenth-century German context of Kant’s Critical philosophy and shows that a number of prominent Kantian doctrines can be seen as growing out of discussions of Aristotelian ideas in philosophers such as Wolff and Crusius. These include the idea that there are three fundamental operations of the mind (the tres operationes mentis), that the mind is an “entelechy,” and that the operations of a rational mind are characterized by spontaneity.

It is claimed that the form of perceiving is mirroring and also map-like. Historically, mirroring is here considered to be akin to mirroring in Leibniz, by whom Kant was influenced. Mirroring can also be taken to be indirect, by way of a representative, as in Locke, according to the standard interpretations. However, it follows from the immediacy condition on perceptions that the mirroring has to be direct in Kant. He also explicitly attacks picture theories of perception. Perceptions are not of an intermediary to be perceived. Rather, they are themselves space-like in their mereological organization, and they represent by way of a structural similarity with the layout of spatial scenes. On this point, it is claimed that Kant’s version of non-conceptualism has similarities with positions in current debates on perception, like those of Fodor and Peacocke. Indeed, perceptions also map the territory, as in Burge, and that goes a bit beyond mirroring. Thus, some features of cartographic representation carry over to intuitions in Kant. Finally, the relation between the saturation of intuitions and the fact that they mirror and map what they represent is discussed.

Suárez offered a rich analysis of three types of distinction, which continued to be important in early modern philosophy: the conceptual distinction (distinction of reason), the real distinction, and the modal distinction. They are commonly understood in terms of separability, but for Suárez, separability was merely a sign of specific types of distinctions. And he argued that mutual separability is neither necessary nor sufficient for a real distinction. Furthermore, he required knowledge of actual cases of mutual separation as a sign of real distinction. This chapter examines the real distinction and modal distinction in early modern philosophy. Descartes inherited Suárez’s view that separability is a mere sign and examination of Suárez’s theory results in elegant solutions to thorny problems in Descartes’s theory of body. Finally, the notion of a mode played an important role in arguments for immaterial beings in Descartes and various other early modern philosophers, including Leibniz.

This chapter looks at Kant’s understanding of the relationship between laws of nature and those of freedom in order to further explain Kant’s grounding argument at 4:453. The two sets of laws constitute two systems, the first governing phenomenal nature and the second the intelligible world, that is, the systematic interrelation of rational wills. How the two sets of laws relate reveal one fundamental philosophical system that can be grasped correctly only from the standpoint of practical reason, namely, that of the agent making use of its intelligence in its practical activity. It is the same understanding and the very same transcendental subject who gives the law to nature, who also gives the law to itself, using the same set of concepts, only differently applied. Our law-giving function in both worlds grounds the primacy of our membership in the intelligible world. Different criteria of application of these concepts to noumenal and phenomenal worlds are discussed, and I show how Kant avoids objections to the idea of timeless agency. Kant espouses a modified Leibizianism through which the intelligible and sensible worlds are harmonized indirectly by the author of nature, who harmonizes the functions in us through which the two are constituted.

Leibniz defends teleology or purposive activity against the overly mechanical worldview of Thomas Hobbes, and develops an idea of spontaneity as self-originating action irreducible to mere mechanistic reaction. He links free activity with justice as the enabling conditions for the exercise of freedom, and with the progressive deployment of individual and collective powers. He thus sets the agenda for subsequent idealism, which reconfigures the idea of spontaneity and reflects on the harmonisation of diverse individual efforts as a problem of ongoing juridical reform

Leibniz is the genuine initiator of German Idealism, developing ideas of freedom as spontaneity or self-originating action, and linking freedom with justice and progress in ways that are decisive for Kant and later idealists. Rethinking spontaneity as negative freedom, Kant criticises the paternalistic perfectionism and Enlightened absolutism of Christian Wolff, a distinct development from Leibniz, but opens the way for a new perfectionism of freedom. The origins of perfectionism in Aristotle and the Stoics are surveyed, and the various formulations of post-Kantian perfectionism from Humboldt to Marx are outlined.

Chapter 2 covers elements in Aquinas’s metaphysics and his views on causation as part of the philosophical background for understanding the Five Ways. Attention is given to Aristotle’s explanations of change and his four causes: material, formal, efficient, and final. The chapter then examines Aquinas’s metaphysics of existence and his distinction between essence and existence, which features a contrast between caused and uncaused existence prominent in the Five Ways. There is a brief look at some more recent views of existence influenced by Immanuel Kant and others, which call Aquinas’s views into question. Finally, the chapter explains Aquinas’s model of explanation, that is, his views on what needs accounting for and how it is to be done. (There is some contrast with Gottfried Wilhelm Leibniz’s views.) Aquinas seeks a complete account for why contingently existing individual objects exist at all and undergo changes. He thinks that what has caused existence must ultimately be accounted for by what has uncaused existence.

The final two Metaphysical Expositions argue that our original representation of space must be intuitive. I draw some surprising connections between Kant’s discussion and Leibniz’s account of the continuum. These connections indicate that the point of Kant’s analysis of <space> is to show that our original representation of space is infinitely complex in content. Since no discursive representation can be infinitely complex, our concept <space> cannot derive its content from discursive spontaneity. Its content must rather be given to the mind in order to be thought at all and thus originates in receptive intuition. Kant’s argument does not hinge on the singularity or holistic structure of space, as many hold, but on its infinite complexity and consequent givenness. I develop a novel account of the discursivity of conceptual representation that preserves the validity of Kant’s argument, defend Kant’s account of the infinity of space against prominent objections, and finally indicate how Kant’s argument entails the singularity of intuition (rather than presupposing it).

In this chapter, we consider a group of philosophers who formed their views in opposition to voluntarist natural law. Although there are important differences between Spinoza, Cudworth, Shaftesbury, and Leibniz, all four were united by their opposition to voluntarism. For voluntarists, even natural law is a kind of positive law since it is created by God’s discretionary imposition. Against this, Cudworth complained that voluntarism makes morality “positive, arbitrary and factitious only” and unable to explain morality’s “eternal and immutable” character. Leibniz was also a critic of positivist law, and he subversively reinterprets law in terms of love. Justice, he says, is the “charity of the wise.” For his part, Spinoza opposes not just positivist law but law itself. Indeed, although his great metaphysical work is titled Ethics, it constitutes nothing less than a metaphysical reduction of ethical or normative categories. At the same time, he develops a deeply attractive account of human freedom that inspired thinkers to come (including Nietzsche). Shaftesbury draws mostly from Cudworth, but in a way that gives rise to the moral sense tradition of Hutcheson, Hume, and Smith.