Anguish is no more than one form of the spiritual experience of the philosopher. In proportion as he goes forward, the philosopher moves through other states: he knows the intellectual joy (into which nothing human penetrates) of decisive intuitions and illuminating certainties--a sort of intoxication with the object that is almsot cruel--and sometimes the freezing exaltation of the glance that denudes and destroys; and sometimes the revulsion of handling those animal skeletons and bones of the dead of which Goethe speaks; and sometimes the ardour which wounds him on every side for the infinite search which men carry on and for all captive truths; sometimes the pity for error with its ambiguities; and sometimes the great solitude or distress of the spirit; and sometimes the sweetness of going forward in the maternal night. What I should like to stress is that the spiritual experience of the philosopher is the nourishing soil of philosophy; that without it there is no philosophy; and that, even so, spiritual experience does not, or must not, enter into the intelligible texture of philosophy. The pulp of the fruit must consist of nothing but the truth.
Jacques Maritain, Existence and the Existent. Image (Garden City, NY: 1948) p. 151.