Immanuel Kant

Metaphysics is a dark ocean without shores or lighthouse, strewn with many a philosophic wreck.
Immanuel Kant - FUNDAMENTAL PRINCIPLES OF THE METAPHYSICS OF ETHICS
To be beneficent when we can is a duty; and besides this, there are many minds so sympathetically constituted that, without any other motive of vanity or self-interest, they find a pleasure in spreading joy around them, and can take delight in the satisfaction of others so far as it is their own work. But I maintain that in such a case an action of this kind, however proper, however amiable it may be, has nevertheless no true moral worth, but is on a level with other inclinations. ... For the maxim lacks the moral import, namely, that such actions be done from duty, not from inclination.

So act that your principle of action might safely be made a law for the whole world.

The history of the human race, viewed as a whole may be regarded as the realization of a hidden plan of nature to bring about a political constitution, internally, and for this purpose, also externally perfect, as the only state in which all the capacities implanted by her in mankind can be fully developed.

From timber so crooked as that from which man is carved, nothing entirely straight can be made.

That all our knowledge begins with experience, there is indeed no doubt....but although our knowledge originates WITH experience, it does not all arise OUT OF experience.
Immanuel Kant - CRITIQUE OF PURE REASON
Human reason has this peculiar fate that in one species of its knowledge it is burdened by questions which, as prescribed by the very nature of reason itself, it is not able to ignore, but which, as transcending all its powers, it is also not able to answer.
Immanuel Kant - FUNDAMENTAL PRINCIPLES OF THE METAPHYSICS OF ETHICS
...as to moral feeling, this supposed special sense, the appeal to it is indeed superficial when those who cannot think believe that feeling will help them out, even in what concerns general laws: and besides, feelings which naturally differ infinitely in degree cannot furnish a uniform standard of good and evil, nor has any one a right to form judgments for others by his own feelings...

So act that your principle of action might safely be made a law for the whole world.
Immanuel Kant - CRITIQUE OF PURE REASON
Criticism alone can sever the root of materialism, fatalism, atheism, free-thinking, fanaticism, and superstition, which can be injurious universally; as well as of idealism and skepticism, which are dangerous chiefly to the Schools, and hardly allow of being handed on to the public.
Immanuel Kant - CRITIQUE OF PURE REASON
"Human reason is by nature architectonic."

Science is organized knowledge. Wisdom is organized life.
Immanuel Kant - The Science of Right
The universal and lasting establishment of peace constitutes not merely a part, but the whole final purpose and end of the science of right as viewed within the limits of reason.

Have patience awhile; slanders are not long-lived. Truth is the child of time; erelong she shall appear to vindicate thee.

Ours is an age of criticism, to which everything must be subjected. The sacredness of religion, and the authority of legislation, are by many regarded as grounds for exemption from the examination by this tribunal, But, if they are exempted, and cannot lay claim to sincere respect, which reason accords only to that which has stood the test of a free and public examination.
Immanuel Kant - FUNDAMENTAL PRINCIPLES OF THE METAPHYSICS OF ETHICS
Act as if the maxim of your action were to become through your will a general natural law
Immanuel Kant - Critique of Practical Reason
The inscrutable wisdom through which we exist is not less worthy of veneration in respect to what it denies us than in respect to what it has granted.

- Immanuel Kant