Immanuel Kant (1724–1804) was perhaps the most profound thinker of that period of modern history known as the Enlightenment, or the Age of Reason. Kant has also arguably been the philosophical figure who has had the greatest overall influence on the subsequent development of Western philosophy from the late eighteenth century to the present day. This introduction will provide just a few details of Kant's biography and discuss some of the more important intellectual influences on his philosophical development, followed by a few remarks on the text of the Critique of Pure Reason. The proper explanation of Kant's philosophical views and of such terms used below as ‘metaphysics’, ‘a priori knowledge’, ‘rationalism’ and ‘empiricism’ will begin in Chapters 1 and 2. For an in-depth and up-to-date biography of Kant, one that simultaneously makes for good reading and explains Kant's personal and philosophical development, I particularly recommend Manfred Kuehn's Kant: A Biography (2001), to which I am indebted here; and see also Ernst Cassirer's earlier Kant's Life and Thought ([1918] 1981).

A BRIEF SKETCH OF KANT'S LIFE AND THE HISTORICAL CONTEXT

‘Emanuel’ (later changed by Kant to ‘Immanuel’) Kant was born on 22 April 1724, in the city of Königsberg, which today is Kaliningrad, Russia, located on the Baltic Sea between Poland and Lithuania. During Kant's life, Königsberg was the capital of East Prussia under the rule of Frederick William I, King of Prussia until 1740, whose reign was followed by Frederick II (‘Frederick the Great’) until 1786, Frederick William II until 1797, and Frederick William III until 1840.

HUME'S SCEPTICISM AND THE PROBLEM OF SYNTHETIC A PRIORI JUDGMENTS

In a famous passage from the Prolegomena to any Future Metaphysics (1783), a shorter (but no less difficult) book in which Kant attempted to restate the central themes of his Critique of Pure Reason, Kant writes that it was in fact his taking in points made by the Scottish philosopher and moderate sceptic David Hume that stimulated the ‘critical’ revolution in his own thinking (cf. A758–69/B786–97):

(On the translation of ‘Erinnerung’, see Beck [1969: 439]; Guyer [2008: 1].) One of the main aims of the Critique of Pure Reason, as we have seen, is to demonstrate that speculative metaphysics has never been based on a sufficiently self-critical prior scrutiny of the essential nature and limits of human reason itself. From this critical perspective Kant characterizes the philosophical doctrines of so-called pre-Critical rational metaphysicians as dogmas of pure reason, and he gives the otherwise estimable thinkers who defended such doctrines the unflattering title of dogmatists (Aix-x; cf. Bxxxv).

APPLYING CATEGORIES TO THE WORLD IN THE PRINCIPLES OF PURE UNDERSTANDING

Let us begin our explanation of Kant's Principles of Pure Understanding with a partial formulation of the result of the Transcendental Deduction in terms of the following conditional. This conditional expresses Kant's idea, discussed in the previous chapter, that the categories are shown to be objectively valid in so far as they are shown to be conditions that are necessary for the possibility of experience:

With respect to the left-hand side of this conditional, in the previous chapter we saw that Kant's analysis of what is to be meant by ‘experience’ is conducted from several different directions, but in particular it involved the concept of an object of sensory experience for a potentially self-aware experiencer. With respect to the right-hand side, we saw that the categories succeed in representing an objective world by being rules or laws that determine what is necessary and possible for the objects that are thereby represented.

Kant pulls no punches in the passage above. Certainly outside philosophy – for that matter, even inside philosophy – it must strike us as counter-intuitive to assert that spatial properties such as size, shape, location and distance are correctly attributed to, and hence possessed by, material bodies “only from the human standpoint”. For when we human beings speak truly about or mathematically represent the fact, for example, that a certain planet's average distance from the sun is approximately 5,869,660,000 kilometres, what is thereby represented is a fact about the spatial layout and temporal history of the material universe. And that is a fact that obtained long before any human beings intruded on the scene. Kant's ‘transcendental idealism and empirical realism’, as we saw in Chapters 1 and 2, is supposed to be compatible with any and all such empirical discoveries about the vast and limitless ‘age and size’ of the material universe in space and time.

The aim of this book is to provide a clear introduction to the central arguments of the Critique of Pure Reason at a level designed for both undergraduate and graduate students as well as any other readers interested in the main contentions and arguments of Kant's revolutionary book. In order to achieve a relatively fluid and readable introduction to such a notoriously difficult text, it was agreed to limit the scholarly engagement with other commentaries and with disputes in the secondary literature to just the occasional in-text reference to particularly influential recent contributions by (primarily English-language) commentators on Kant, without any apparatus of notes. I have also had to make decisions about which sections of the book to treat in depth and which to treat more briefly, and the index is the way to locate the latter discussions. Within the restricted scope of this book, however, what follows is not a superficial introduction to Kant's thought but rather an attempt to analyse, explain and assess the main lines of argument that occur in most of the more famous sections of the Critique. In places in each chapter I have also taken matters more deeply and have not held back from offering my own reconstructive interpretations of Kant's views, some of which may be of interest to more experienced readers of Kant.

There are many high-quality commentaries on Kant's Critique of Pure Reason currently available in English, some of which are listed in the Bibliography, so that one has to feel some trepidation in offering a new one. In my experience of teaching and writing on the Critique over the past twenty-five years, however, it is remarkable how many students, lecturers and professors continue to express the desire for a comparatively short and introductory but non-superficial explanation of Kant’s fundamental conceptions and interconnected strategies of argumentation in the Critique.

CONCEPTUAL THINKING: THE CATEGORIES AS A PRIORI FORMS OF UNDERSTANDING

The need for a transcendental deduction of the categories

In the previous chapter we examined Kant's novel contention in the Transcendental Aesthetic that even our most basic sensory capacities already presuppose certain pure a priori dimensions of human cognition that are not themselves derived from sensation a posteriori. These are the universal frameworks of space and of time as pure forms of our outer and inner sensory intuition. According to Kant, we human beings can have knowledge of objects only if they are given to us, directly or indirectly, by affecting our receptive faculty of sensibility. The resulting sensory intuitions of objects are immediate and singular presentations of particular objects, such as a visual intuition of the Eiffel Tower from a certain perspective or point of view.

CLIPPING THE WINGS OF PURE SPECULATIVE REASON

Kant's overriding emphasis in the First Critique is on the need for a critique of pure reason: that is, for a strict intellectual disciplining (see “The Discipline of Pure Reason”, 738/B766ff.) of the overreaching pretensions of the lofty and inevitable ideas and ideals of our totalizing rational faculty.