Immanuel Kant (22 April 1724 - 12 February 1804) was a German philosopher during the European enlightenment, working primarily in the field of metaphysics. His most prominent contributions to contemporary thought are his theories of metaphysics and epistemology, as well as ethics. In apologetics, Kant proposed serious objections to the ontological argument.
Philosophical and Theological Contributions
Kant's contributions to metaphysics and epistemology are often given secondary importance to the conception. However, his contributions to those fields were significant, as well as his contributions to ethics.
The thing in itself
Kant argues that there is a distinction between the external world (the "thing in itself" or the "noumenal" world) and the way we perceive it (phenomenon). As an analogy:
- "imagine if everyone on earth wore green-tinted sunglasses, all the time. To them, everything would look green. In fact, if they didn't know they were wearing sunglasses, and if they had absolutely no way of taking them off, then as far as they were concerned, the world would be, objectively, green. As it might be with green sunglasses, says Kant, so it is that our brains impose certain things on the way we perceive the world. Things like space, time, logic and mathematics... And in fact, it's impossible to conceive of an outside world that's truly independent of the way we perceive it - just as no-one in the green sunglasses world would be able to conceive of a non-green colour."
Or in Kantian jargon:
- "that the noumenal world may exist, but it is completely unknowable through human sensation "
- "Kant commits the same error as Hume-he violates the Law of Noncontradiction. He contradicts his own premise by saying that no one can know the real world while he claims to know something about it, namely that the real world is unknowable! [...] What we are saying is that you really do know the thing in itself. You really do know the tree you are seeing, because it is being impressed on your mind through your senses."
The point is we could be biased by our perceptions, not Kant claims we definitely are biased. Saying we know for sure that Kant is wrong, and that Naïve realism is true, would require evidence or argument beyond what the apologist has said, and they have the burden of proof. Just showing that Kant does not know for certain does not prove their point that Naïve realism is true.
Categories of knowledge
Kantian epistemology focuses on a distinction between two categories of statement, the synthetic and the analytic. Though Kant did not use this language, the two are often expressed as being properties of propositions. An analytic proposition is one which can be found to be true or false without reference to any other statement. A synthetic proposition is one which can only be found to be true or false with to other statements. Kant also distinguishes between statements which can be known to be true a priori and those which can only be known to be true a posteriori. A statement can be known to be true a priori if the discernment of its truth value can be assessed without any investigation of the physical world. A posteriori statements can only be found to be true or false upon observation of the physical world.
- Main Article: Categorical imperative
The most popular idea attributed to Kant is his conception of the 'categorical imperative', which he regarded as a means for assessing the viability of a statement as a potential moral law. That moral law, if it was found to be in compliance with the categorical imperative, could then be applied to maxims, or moral statements about the value of a particular action at a particular time. It can be found, in three formulations, in Groundwork for the Metaphysics of Morals.
The first formulation is popularly rendered as: Always act according to that maxim that you can at the same time will would become universal law. Kant did assert that there were certain acts which it was always necessary to do, in accordance with this imperative. Among these, a popular example which was, in his own time, criticized, was 'telling the truth', which Kant maintained an individual was always morally obliged to do.
The second formulation is popularly paraphrased as: See all rational beings not simply as means to achieve ends, but as ends in themselves. There are some concerns that have been raised by ethicists about what is regarded as a 'rational being', and what prescribed relationship such a maxim would entail, or permit, with respect to non-rational beings.
The third formulation is popularly rendered: All maxims which stem from autonomous legislation ought to harmonize with a possible realm of ends as with a realm of nature. It is generally regarded as a sort of synthesis, or middle-ground, between the first and second formulations.
(1781) Critique of Pure Reason
(1788) Critique of Practical Reason
(1790) Critique of Judgment
(1797) Metaphysics of Morals