For the sake of its own perfection, therefore, the spiritual life must continually turn back to the realm of experience, from which, at first, it tore itself free. Attempts to evolve the whole life from that _a priori_ have always given as a result something of a bloodless nature, abstract in the highest degree, a mere web of formulæ, in so far as experience, which had been relegated to the background, has not indirectly asserted its right again, and infused the formulæ with life. Accordingly, our life does not spend itself in one direction, but bears within it the counter-tendencies of a tearing oneself free from the world of sense and a returning back to it, of a detachment from it and an appropriation of it to oneself. But, in this, independent life and bound life do not become combined; how could that be the case without the loss of all inner unity? A basis is necessary; and it is furnished only by self-determining activity. Experience acquires a spiritual content and value only so far as it is based upon this activity, and is taken up into a spiritual movement. Experience does not share something with the spiritual life, but, through stimulation and opposition, it forces that life to further development within itself. The state in which the world of sense is first found undergoes an inner elevation in that appropriation: sense presentation, for example, is to scientific work something quite different from what it is to naïve perception; even if it obstinately withstands a complete resolution into magnitudes of pure thought, it takes up more and more thought elements; it enters into conceptual relations; it answers questions which the work of thought sets. To the whole sphere of sense science gives the background of a world of thought, and transforms mere sense into a spatially bound spirituality.