Immanuel Kant

Immanuel Kant (1724-1804), a German, was one of the greatest philosophers of all time. His Critique of Pure Reason, though very difficult to read, created a revolution in philosophy by arguing that the world is knowable by us only because our minds give it the shape and structure it has. He solved most of the major problems of both Rationalism and Empiricism and sent philosophy in a new direction. His ethical theory was especially profound, And he is famous for his categorical imperative: Treat others as ends always, never as means only.

Two things fill the mind with ever new and increasing admiration and awe ... the starry heavens above and the moral law within.
- Immanuel Kant

What then are time and space? Are they real existences? Or, are they merely relations or determinations of things, ... or are they such as belong only to the form of intuition, and consequently to the subjective constitution of the mind...?
- Immanuel Kant, Critique of Pure Reason (1781. J. M. D. Meikeljohn translation,1855)