H. S. Lewis - Wisdom of the Sages - Thou shall desire wisdom with a heart free from doubt
The very first command in the decalogue of the Law of Selection is:
THOU SHALT DESIRE WISDOM WITH A HEART FREE FROM DOUBT!
Doubt is, and always has been, the poisoned spear of the Evil One, with which he prods us on in our inquiries and searches, but tortures us so greatly that naught is finally desired but relief from the poison of the specific anxiety. Doubt leads us through a long, dark passageway toward that door where we anticipate finding light, and rejoices in the fact that it keeps us in darkness and prevents us from perceiving the many, many doorways which we pass unnoticed and unknown.