I am currently reading Schiller so as to better understand the groundwork of Max Weber's die Entzauberung der Welt [the disenchanted world]. Weber borrowed this image from Schiller. So, in today's reading of Schiller's Eighth Letter in his 'On The Aesthetic Education of Man', I came across this wonderful little nugget:
Reason has accomplished all she can in discovering and expounding the law. It is the task of the courageous will and lively feeling to put it into execution. If truth is to gain the victory in the struggle with force, she herself must first become a force and appoint some drive as her representative in the realm of phenomena; for drives are the only motive forces in the sensible world. That up to now truth has displayed so little of her victorious strenth is due not to the intellect which was incapable of unveiling it, but to the heart which remained closed to it and to the impulse which refused to act in her behalf.
Friedrich Schiller. 'On the Aesthetic Education of Man,' in Anthology for our Time (New York: Frederick Ungar Publishing, 1959), p. 221.