Introduction To Christianity - pg. 33

This means that the old equation of truth and being is replaced by the new one of truth and factuality; all that can be known is the "factum", that which we have made ourselves. It is not the task of the human mind - nor is it within its capacity - to think about being, but about the factum, what has been made, man's own particular world, for this is all we can truly understand. Man did not produce the cosmos and its bottommost depths remain opaque to him. Complete, demonstrable knowledge is attainable only within the bounds of mathematics and in the field of history, which is the realm of man's own activities and can therefore be known by him. In the midst of the sea of doubt which threatened to engulf man at the beginning of the modern period after the collapse of the old metaphysics, the factum was here discovered as the dry land on which man could try to build a new existence for himself. The dominance of fact began, that is, man's complete devotion to his own work as the only certainty.