In Kant's essay "Answering the Question: What is Enlightenment?",
he defined the Enlightenment as an age shaped by the Latin motto Sapere aude ("Dare to be wise").
Kant maintained that one ought to think autonomously, free of the dictates of external authority.
His work reconciled many of the differences between the rationalist and empiricist traditions of the 18th century.
He had a decisive impact on the Romantic and German Idealist philosophies of the 19th century.
His work has also been a starting point for many 20th century philosophers.

Kant asserted that, because of the limitations of argumentation in the absence of irrefutable evidence, no one could really know whether there is a God and an afterlife or not.
For the sake of morality and as a ground for reason, Kant asserted, people are justified in believing in God, even though they could never know God's presence empirically.

Thus the entire armament of reason, in the undertaking that one can call pure philosophy, is in fact directed only at the three problems that have been mentioned [God, the soul, and freedom].
These themselves, however, have in turn their more remote aim, namely, what is to be done if the will is free, if there is a God, and if there is a future world.
Now since these concern our conduct in relation to the highest end, the ultimate aim of nature which provides for us wisely in the disposition of reason is properly directed only to what is moral.

The sense of an enlightened approach and the critical method required that "If one cannot prove that a thing is, he may try to prove that it is not.
If he fails to do either (as often occurs), he may still ask whether it is in his interest to accept one or the other of the alternatives hypothetically, from the theoretical or the practical point of view.
Hence the question no longer is as to whether perpetual peace is a real thing or not a real thing, or as to whether we may not be deceiving ourselves when we adopt the former alternative, but we must act on the supposition of its being real."
The presupposition of God, soul, and freedom was then a practical concern, for
Morality in itself constitutes a system, but happiness does not, except insofar as it is distributed precisely in accordance with morality.
This, however, is possible only in the intelligible world, under a wise author and regent.
Reason sees itself as compelled either to assume such a thing, together with life in such a world, which we must regard as a future one, or else to regard the moral laws as empty figments of the brain ...
Kant drew a parallel between the Copernican revolution and the epistemology of his new transcendental philosophy, involving two interconnected foundations of his "critical philosophy": 
the epistemology of transcendental idealism and
the moral philosophy of the autonomy of practical reason.

These teachings placed the active, rational human subject at the center of the cognitive and moral worlds.
Kant argued that the rational order of the world as known by science was not just the accidental accumulation of sense perceptions.

Conceptual unification and integration is carried out by the mind through concepts or the "categories of the understanding" operating on the perceptual manifold within space and time.
The latter are not concepts, but are forms of sensibility that are a priori necessary conditions for any possible experience.
Thus the objective order of nature and the causal necessity that operates within it depend on the mind's processes, the product of the rule-based activity that Kant called, "synthesis."
There is much discussion among Kant scholars about the correct interpretation of this train of thought.

The 'two-world' interpretation regards Kant's position as a statement of epistemological limitation, that we are not able to transcend the bounds of our own mind, meaning that we cannot access the "thing-in-itself".
However, Kant also speaks of the thing in itself or transcendental object as a product of the (human) understanding as it attempts to conceive of objects in abstraction from the condition
In Kant's essay "Answering the Question: What is Enlightenment?", he defined the Enlightenment as an age shaped by the Latin motto Sapere aude ("Dare to be wise"). Kant maintained that one ought to think autonomously, free of the dictates of external authority. His work reconciled many of the differences between the rationalist and empiricist traditions of the 18th century. He had a decisive impact on the Romantic and German Idealist philosophies of the 19th century. His work has also been a starting point for many 20th century philosophers.
Kant asserted that, because of the limitations of argumentation in the absence of irrefutable evidence, no one could really know whether there is a God and an afterlife or not. For the sake of morality and as a ground for reason, Kant asserted, people are justified in believing in God, even though they could never know God's presence empirically.
Thus the entire armament of reason, in the undertaking that one can call pure philosophy, is in fact directed only at the three problems that have been mentioned [God, the soul, and freedom]. These themselves, however, have in turn their more remote aim, namely, what is to be done if the will is free, if there is a God, and if there is a future world. Now since these concern our conduct in relation to the highest end, the ultimate aim of nature which provides for us wisely in the disposition of reason is properly directed only to what is moral.
The sense of an enlightened approach and the critical method required that "If one cannot prove that a thing is, he may try to prove that it is not. If he fails to do either (as often occurs), he may still ask whether it is in his interest to accept one or the other of the alternatives hypothetically, from the theoretical or the practical point of view. Hence the question no longer is as to whether perpetual peace is a real thing or not a real thing, or as to whether we may not be deceiving ourselves when we adopt the former alternative, but we must act on the supposition of its being real." The presupposition of God, soul, and freedom was then a practical concern, for
Morality in itself constitutes a system, but happiness does not, except insofar as it is distributed precisely in accordance with morality. This, however, is possible only in the intelligible world, under a wise author and regent. Reason sees itself as compelled either to assume such a thing, together with life in such a world, which we must regard as a future one, or else to regard the moral laws as empty figments of the brain ...
Kant drew a parallel between the Copernican revolution and the epistemology of his new transcendental philosophy, involving two interconnected foundations of his "critical philosophy": 
the epistemology of transcendental idealism and
the moral philosophy of the autonomy of practical reason.
These teachings placed the active, rational human subject at the center of the cognitive and moral worlds. Kant argued that the rational order of the world as known by science was not just the accidental accumulation of sense perceptions.
Conceptual unification and integration is carried out by the mind through concepts or the "categories of the understanding" operating on the perceptual manifold within space and time. The latter are not concepts, but are forms of sensibility that are a priori necessary conditions for any possible experience. Thus the objective order of nature and the causal necessity that operates within it depend on the mind's processes, the product of the rule-based activity that Kant called, "synthesis." There is much discussion among Kant scholars about the correct interpretation of this train of thought.
The 'two-world' interpretation regards Kant's position as a statement of epistemological limitation, that we are not able to transcend the bounds of our own mind, meaning that we cannot access the "thing-in-itself". However, Kant also speaks of the thing in itself or transcendental object as a product of the (human) understanding as it attempts to conceive of objects in abstraction from the condition
Immanuel Kant