"From my 'The Philosophy of Spiritual Activity' you will know that the highest ethical ideas required by us as human beings are given to us when we grasp moral intuitions, and that when we begin to gain possession of these ethical ideas, they are the foundation of our human freedom. On the other hand, you may perhaps also know that for certain thinkers there has always been a kind of abyss between that which is given, on the one hand, by the knowledge of Nature, and on the other hand, by ethical knowledge. The philosophy of Kant is based upon this abyss, which he is unable to bridge completely. For this reason, Kant has written a Critique of Theoretical Reason, of Pure Reason, as he calls it, where he grapples with natural science, and where he says all that he has to say about natural science, or the knowledge of Nature. On the other hand, he has also written a Critique of Practical Reason, where he speaks of ethical ideas. We might say: The whole human life is born for him out of two roots which are completely severed from one another, which he describes in his two chief critical studies."
Rudolf Steiner - Fundamentals of the Science of Initiation - October 17, 1919