Descartes on God

Descartes says in his meditations that all truth depends on God. He even goes as far to say that it would be possible for God to change the principles of mathematics and make 2 + 2 not equal 4. This seems strange to me and im sure no modern philosopher would tie so much of their theories of truth and knowledge with religion but its still interesting to see how closely tied knowledge and religion once was. Now it could b e explained that Descartes did this only so that his work would not cause him to be excommunicated from the church, but he seems genuine in his beliefs. Its interesting to think about though.