What was Immanuel Kant's Copernican Revolution?

Just as Copernicus changed the center of our universe from Earth to Sun, Kant relocated the basic principles and categories of reality, as studied by science, from the external world to the mind. Like John Locke (1632-1704), he began with an examination of the powers of the mind and an aim to reject metaphysical claims that could not be rationally justified. He posited a human rational necessity to understand real experience in space and time and a practical need to live with other rational beings, seeking the principles that could fulfill those requirements.

In 1770 Kant argued in On the Form and Principles of the Sensible and Intelligible World that our knowledge of space and time is only about appearances, but that we are still justified in making limited claims about what lies behind those appearances. This was the foundation for what became known as critical philosophy. Kant's revolutionary claim was that we have a priori knowledge of both space and time because they are the forms of our perception: space is the organization of experience in the outer world, while time is the organization of experience in the inner world. (This was followed by the two editions of his Critique of Pure Reason, with his Prolegomena to any Future Metaphysics published in between to respond to criticism.)

What was Immanuel Kant's notion of synthetic a priori knowledge?

Knowledge is "synthetic" or "ampliative," according to Kant, if it is about objects that can be experienced in the world. It is a priori if it can be known without experience. Kant's motivating metaphysical question was, "How is it possible to know certain principles about the world, without prior experience?"

Kant's solution was to apply a "transcendental deduction" to such principles and show that without them experience would not be possible. For example, concerning causation, he argued that consciousness itself requires orderly experience based on necessary connections in reality. This was Kant's answer to David Hume's (1711-1776) reduction of causation to constant conjunction. He rejected Hume's skepticism that constant conjunction is all that there is by claiming that the world could only make sense to us if we assumed that that there were real causal connections in it. In his Prolegomena to Every Future Metaphysics (1783), Kant famously said that Hume had awakened him from his "dogmatic slumbers."

What was Immanuel Kant's moral system?

Kant's moral starting point is the distinction between things that are instrumentally or hypothetically good because they have good consequences, and things that are good in and of themselves. The only thing that is good in itself is a good will or benevolence, without which every other gift of fortune can be just cause for resentment. Morality is for rational beings, and rational beings require principles of action. In the community of rational beings, or the Kingdom of Ends, actions are good if they are autonomous, which is to say freely chosen.

According to Kant, a rational being is autonomous or self-ruling. The rules that a rational being uses to regulate himself are absolute—what Kant called "categorical." Such rules are imperatives and are followed for their own sake. Hypothetical rules, by contrast, are followed in order to make something else happen. For example, "Do not harm innocent people" would be a categorical rule and "Eat your vegetables" would be a hypothetical rule.

What was Immanuel Kant's categorical imperative?

Kant is usually interpreted to have two formulations. First, "Act so that the maxim of your action, or the generalization describing it, can be willed by you to be a general rule, to be followed by all rational agents." In other words, only do those things that you as a benevolent, rational being can will that everyone do.

The test of a categorical imperative is what happens if everyone follows it. Something that has good consequences in a particular case might not have good consequences in all cases. For example, if the maxim is "Obey traffic rules," and you come to a red light with no other cars in attendance, you may not drive through it, even though the consequences in this particular case would be benign. Or, to use an example of Kant's, if the maxim is not to lie, and a madman is looking for a friend of yours whose whereabouts you know, you may not lie in this case, because overall you can't benevolently will that everyone be permitted to lie whenever the consequences are good for them. To take another example of Kant's, you may not take your own life, no matter how miserable you are, because you categorically can't will suicide as a good action.

Was Immanuel Kant a recluse?

Yes. He lived a very precise and orderly life, and his neighbors claimed to be able to set their clocks by his daily walks. During the 1770s, he retreated into what biographers call his "silent decade." He set himself the task of figuring out how perception and intellect are connected. Never a bon vivant, he withdrew from even minimal social contact. But he was very forthright about what was going on in his life and did not make the usual social excuses. When a former student tried to coax him out, he responded in this manner:

Any change makes me apprehensive, even if it offers the greatest promise of improving my condition, and I am persuaded by this natural instinct of mine that I must take heed if I wish that the threads which the Fates spin so thin and weak in my case to be spun to any length. My great thanks to my well-wishers and friends, who think so kindly of me as to undertake my welfare, but at the same time a most humble request to protect me in my current condition from any disturbance.

Is Immanuel Kant's categorical imperative different from the Golden Rule?

Yes, it is. According to the Golden Rule, we should act as we would have others act toward us. If our tastes are perverted or we do not care for our own welfare, the Golden Rule could permit acts of depravity and violence, but such acts could never be willed categorically. Moreover, Kant's system is strongly based on individual good will toward the community of all other rational individuals. There is a debt to Jean Jacques Rousseau's (1712-1778) idea of the "common good" here; indeed, Kant greatly respected Rousseau's moral philosophy.

 What was Immanuel Kant's second formulation of the categorical imperative?

According to Kant, all rational beings are intrinsically valuable, and in the Kingdom of Ends, no one is a means to the end of anyone else. In the world of affairs what we do and who we are have prices, but in the Kingdom of Ends there are no prices, only dignities. The second formulation of the categorical imperative is that one must always act to treat humanity (either as another person or oneself) as an end and never as a means. In other words, don't use people!

What was Immanuel Kant's theory of the self?

Kant distinguished between the empirical ego and the transcendental ego. The empirical ego is what we normally think of as the self and are able to experience. The transcendental ego is the necessary origin of those fundamental structures of thought and intuition that are necessary for experience. The transcendental ego is known only as an object of thought, and not as an object of direct experience.

What was Immanuel Kant's proof of God's existence?

Kant rejected the ontological argument on the ground that existence is not a quality or characteristic of things. According to Kant, we cannot say that the sweater is red, wool, and it exists. He rejected the first cause argument as partly relying on the onto-logical argument; and he rejected the argument from design on the grounds that, at best, it proves only an architect or designer of the universe, and not a creator. Kant himself thought there was a moral proof for God's existence because the moral agent knows that he cannot achieve his goals on his own without God. The resulting belief in God becomes a matter of individual, personal conviction—not "It is morally certain that there is a God," but "I am morally certain that there is a God."