The teachings of Jesus Christ were at once profound and paradoxically simple. Christ did not address Himself to intellectuals; His intention was to bring a message of salvation to all men – the unlearned and the learned, the rich and the poor, the sick and the healthy. Almost form the beginning of Christianity, however, some men attempted intellectually to penetrate and analyze the Christian message, and to ask that fundamental question – Why? – of all its phases. Christ did not teach a metaphysics, epistemology, or ethics. But what He did teach stimulated the intellectually inclined to speculate about the nature of reality, of knowledge, of the good, and of the beautiful. In short, some men found that philosophical approach was necessary to their intellectual appreciation of the good news of Christianity. These men were the theologians, and it is for this reason that they are sometimes called philosophers, and at other times Christian philosophers.
Robert P. Goodwin, “General Introduction” from Selected Writings of St. Thomas Aquinas