Immanuel Kant (1724-1804) is commonly known as the greatest of modern philosophers. However, in his book A History of Western Philosophy, Bertrand Russell comments that he cannot ‘agree with this estimate’ but that it would be foolish not to recognise his great importance. Russell considers Kant ‘the founder of German idealism’ but ‘not himself politically important’, even though he wrote some interesting essays on political subjects.
Brought up as a pietist, Kant was a Liberal both in politics and in theology and he sympathised with the French Revolution until the Reign of Terror. He was a believer in democracy.
Russell explains how his philosophy ‘allowed an appeal to the heart against the cold dictates of theoretical reason’. His principle that every man is to be regarded as an end in himself is a form of the doctrine of the Rights of Man; and his love of freedom is shown in his saying (about children as well as adults) that “there can be nothing more fearful than that the actions of a man should be subject to the will of another”.
Kant’s most important book is The Critique of Pure Reason. Until its publication in 1781, it might have seemed as if the older philosophical tradition of Descartes, Spinoza, and Leibniz were being overcome by the newer empirical method. However Russell explains how this newer method had never prevailed in German universities, and after 1792 it was held responsible for ‘the horrors’ of the Revolution.
Kant gave rise to a movement which he would have detested for the simple reason that he was a liberal, a democrat and a pacifist – yet those who professed to develop his philosophy were not.
Russell recounts how Kant believed that he had made a synthesis of the philosophy derived from Descartes and that derived from Locke; but that this cannot be admitted, at least from a historical point of view, for the followers of Kant were in the Cartesian, not the Lockean, tradition.
From Descartes to Kant, Continental philosophy derived much of its conception of the nature of human knowledge from mathematics, but regarded mathematics as known independently of experience.
A selection of Kant’s theories set forth in his Critique of Pure Reason:
Kant believes that none of our knowledge can transcend experience but it is, nevertheless, in part a priori and not inferred inductively from experience. The part of our knowledge which is a priori embraces not only logic, but much that cannot be inducted in logic or deduced from it. He separates two distinctions:
- The distinction between analytic and synthetic propositions.
- The distinction between a priori and empirical propositions.
An “analytic” proposition is one in which the predicate is part of the subject (i.e.) “a tall man is a man,” or “an equilateral triangle is a triangle.”
A “synthetic” proposition is one that is not analytic. All the propositions that we know only through experience are synthetic. However, unlike Leibniz (https://brackenstockley.wordpress.com/2013/02/20/hcj-empiricism-and-rationalism-in-the-17th-and-18th-centuries-descartes-spinoza-and-leibniz/), Kant will not admit the converse, that all synthetic propositions are only known through experience.
An “empirical” proposition is one which we cannot know except by the help of sense-perception, either our own or that of someone else whose testimony we accept.
An “a priori” proposition is one which, though it may be elicited by experience, is seen, when known, to have a basis other than experience.
Hume proved that the law of causality is not analytic, and had inferred that we could not be certain of its truth (https://brackenstockley.wordpress.com/2013/03/12/empiricism-locke-to-hume/). Kant accepted the view that it is synthetic, but maintained that it is known a priori. He maintained that arithmetic and geometry are synthetic, but are likewise a priori.
Kant’s solutions to the problem “how are synthetic judgments a priori possible?”
Kant says that the outer world causes only the matter of sensation, but our own mental apparatus orders this matter in space and time, and supplies the concepts by means of which we understand experience. Things in themselves, which are the causes of our sensations, are unknowable; they are not in space or time, they are not substances, nor can they be described by any of those other general concepts which Kant calls “categories”.
Space and time are subjective as they are part of our apparatus of perception. It is because of this that we can be sure that whatever we experience will exhibit the characteristic dealt with by geometry and the science of time. Space and time, Kant says, are not concepts; they are forms of “intuition”.
Kant’s a priori concepts are made up of twelve “categories”, which he derives from the forms of the syllogism.
- Inherence and Subsistence
- Cause and Effect
- Necessity and contingency
These twelve categories are then divided into four sets of three:
(1) Of Quantity: unity, plurality, and totality
(2) Of Quality: reality, negation, and limitation
(3) Of Relation: substance-and-accident, cause-and-effect, reciprocity
(4) Of Modality: possibility, existence, necessity.
Kant set to work to demolish all the purely intellectual proofs of the existence of God. He made it clear that he had other reasons for believing in God; these he was to set forth later in The Critique of Practical Reason.
There are, he says, only three proofs of God’s existence by pure reason:
(1) The Ontological proof
(2) The Cosmological proof
(3) The Physio-theological proof
God, freedom, and immortality, he says, are the three “ideas of reason.” But although pure reason leads us to form these ideas, it cannot itself prove their reality.
Kant’s Theory of Space and Time
In regards to space, Kant’s metaphysical arguments are as follows:
(1) Space is not an empirical concept, abstracted from outer experiences, for space is presupposed in referring sensations to something external, and external experience is only possible through the presentation of space.
(2) Space is a necessary presentation a priori, which underlies all external perceptions; for we cannot imagine that there should be no space, although we can imagine that there should be nothing in space.
(3) Space is not a discursive or general concept of the relations of things in general, for there is only one space, of which what we call “spaces” are parts, not instances.
(4) Space is presented as an infinite given magnitude, which holds within itself all the parts of space; this relation is different from that of a concept to its instances, and therefore space is not a concept but an Anschauung.
The transcendental argument concerning space is derived from geometry. Kant holds that Euclidean geometry is known a priori, although it is synthetic (not deducible from logic alone).