Following a close reading, we have stated in the introduction a discussion of the problem of God in St. Thomas and Hegel. Our research, however, led in another direction. We explore the philosophical background that enters into dialogue with St. Thomas on the existence of God. In this sense, for a better contextualization of Aquinas, we have St. Augustine and St. Anselm stand as two pillars and sources that help inspire a better understanding of the thomistic approach to God. At stake are a priori demonstrations of St. Augustine and St. Anselm and the a posteriori proof of St. Thomas. As part of our investigation, we divided the work into three chapters: the first and second explore general considerations on St. Augustine and St. Anselm from the perspective of faith and reason. Accordingly, we succinctly present what God means for each of them and how this relates to their own experience of God. Then, we focus on the question of the existence of God in everyone, which leads us to the core of our inquiry: to publicize the thomistic philosophical positions about God, present at the beginning of his treatise De Deo Uno. What it claims is the third and final chapter, which allows us to deduce that God is one thing (being immutable and eternal) and that the world is another thing (in constant movement, precisely because of its contingency and finiteness. So being in the world through five ways, we can say that God exists without this proposition is a truth immediately evident. God exist, but