Last week we looked (very) briefly at Medieval thought through the eyes of Anselm, Abelard, and Thomas Aquinas. Now let's run across the bridge from their world to the "modern" era. Make three quick jumps with me.

First we stand on Medieval feet, intellectually. Philosophy is based on authority structures. Revelation comes through the Church. Our primary concern is for the God-man relationship.

Now we jump to the Renaissance. Reason becomes more important than before, as it is shaped through our study of nature and classical literature. Authority structures are deemphasized, the autonomy and enlightenment of mankind is elevated, and concern for the man-man relationship reigns supreme.

Then we jump to the Reformation. Revelation comes not through Church or intellect but Scripture. Authority is found not in Church or man but Scripture. The God-man relationship is crucial once again.

Finally we leap to Rationalism. Reason is the normative means of discovering truth. There is no authority structure outside our reason. Our concern is for the man-man relationship. Here's why.

Rene Descartes (1596-1650) made each of these jumps with us. His was a Jesuit education, coupled with a fascination for mathematics. In light of the Reformation, he wanted to give his beloved Catholic Church a stable and reasonable foundation. In response to the popularity of the Renaissance and its Enlightenment, he felt this foundation must be strongly rational.

So he reasoned as any mathematician would: start from an unquestionable position, then reason to an unassailable conclusion and proof. Using the mathematical premise of doubt, Descartes soon realizes that he can doubt anything he can think of. He can doubt even his own existence. But what is the one fact he cannot doubt? That he is doubting. If he is doubting, by definition he is thinking. Result: "I think, therefore I am" (Cogito, ergo sum, the only Latin words even non-Latin speakers know).

Now Descartes is free (in his own mind) to reason from reason. He thinks he has proven the authority of human reason. So he will apply it to the rest of reality. By rational definition, God is absolute or he is not God (shades of Anselm). He can be the only absolute Substance. Everything else, including mind and body, must be a "relative" substance. God cannot be absolute Substance if he is bound to the material--rather, his existence must be spiritual/intellectual in nature. And God has given us the ability to reason, so that we can be in his "image" and comprehend his creation.

And so God puts in our minds "innate ideas" which give structure to human nature. These structures of rational investigation are the means by which we learn what we know, as they define both truth and relevance. (Unfortunately for his followers, Descartes was never able to relate such a mind to the physical body. In time, this problem would destroy pure rationalism as a philosophy.)

Descartes was sure that his insistence upon reason as the origin and test for truth could be used to demonstrate conclusively the rationality of the Catholic Church in the face of its detractors. But he was wrong. This insistence in time actually worked against the faith he sought to serve. If reason is the test and source of all truth, then why do reasonable people need revelation? The Church? God?