I wrote this as a response to an excellent blog by Andrew Haines on Saint Anselm's ontological proof of God:
Although I agree that Anselm's proof can lead to a greater comprehension of the mystery of God, I think he fails in two respects. First, by relying only on a rational argument and seemingly ignoring the second form whereby man attains to truth (one that "transcends all the industry of reason," as Thomas says) Anselm fails to convince the reader of God's existence. Aquinas' five proofs are far more convincing, not b/c more sound but b/c Aquinas admits to their being not "articles of faith, but... preambles to the articles." The five proofs of Aquinas, consequently, become buttresses for furthering the faith of one who believes, not as bludgeons to force a non-believer into belief.
Second, by using the ontological proof as an airtight argument against which only "a fool" would argue Anselm cuts out the agony of the atheist's struggle. Indeed, the psalm suggests that "the fool in his heart has said, 'there is no God'"; but Aquinas takes this to mean that rejection of the LOGOS (God) makes all thought impossible and thus makes man foolish. This does not, Aquinas notes, make the struggle any less b/c the atheist in struggling to recognize that LOGOS exists realizes his darkness and yet cannot overcome it by his own power. As Thomas notes "(the existence of LOGOS) precisely is not admitted by those who hold that God does not exist." But Aquinas offers a way out for the perplexed by suggesting that "the prime author and mover of the universe is intelligence," before suggesting that he is YHVH or Joshua bar Joseph or any sort of personal god.
Thomas thus shows more mercy to struggling humanity when he states that all men, even "the simple", come to know God through his effects by a slow, gradual process of "(putting) forward divine and spiritual truths by means of comparisons with material things" and not by intelligence alone, lest "the truth about God such as reason could discover, would only be known by a few." Thomas is less elitist, more understanding of human weakness, and thus far more palatable than Anselm in his advocacy for belief.
Thanks again for the thoughts on Anselm which provided for a brief intellectual escape from the cold of Minnesota and the agony of grading essays.