Herman Bavinck on the use of non-Christian philosophy in the service of Christian theology:
Initially the Reformation assumed a hostile posture toward scholasticism and philosophy. But it soon changed its mind. Because it was not, nor wanted to be, a sect, it could not do without theology. Even Luther and Melanchthon, therefore, already resumed the use of philosophy and recognized its usefulness. Calvin assumed this high position from the start, saw in philosophy an “outstanding gift of God,” and was followed in this assessment by all Reformed theologians. The question here is not whether theology should make use of a specific philosophical system. Christian theology has never taken over any philosophical system without criticism and given it the stamp of approval. Neither Plato’s nor Aristotle’s philosophy has been held to be the true one by any theologian. That theologians nevertheless preferred these two philosophical systems was due to the fact that these systems best lent themselves to the development and defense of the truth. Present also was the idea that the Greeks and Romans had been accorded a special calling and gift for the life of culture. Still to this day, in fact, our whole civilization is built upon that of Greece and Rome. And Christianity has not destroyed but Christianized and thus consecrated those cultures. Still, theology is not in need of a specific philosophy. It is not per se hostile to any philosophical system and does not, a priori and without criticism, give priority to the philosophy of Plato or of Kant, or vice versa. But it brings along its own criteria, tests all philosophy by them, and takes over what it deems true and useful. What it needs is philosophy in general. In other words, it arrives at scientific theology only by thinking. The only internal principle of knowledge, therefore, is not faith as such, but believing thought, Christian rationality. Faith is self-conscious and sure. It rests in revelation. It includes cognition, but that cognition is completely practical in nature, a knowing (γιγνώσκειν) in the sense of Holy Scripture. Theology, accordingly, does not arise from believers as such; it is not a product of the church as institution; it does not have its origin in the official ministry Christ has given his church. But believers have still another, fuller life than that which comes to expression in the church as institution. They also live as Christians in the family, the state, and society, and pursue the practice of science and art. Many more gifts than are operative in the offices are granted them, gifts of knowledge and wisdom and prophecy. Among them, too, there are those who feel a strong impulse toward study and knowledge, who have received gifts for apprehending and systematizing the truth of God. Thus theology arises in the church of Christ; its subject is not the institutional church but the church as organism, the body of Christ. It is a product of Christian thinking.
Source: Reformed Dogmatics, Vol. 1: Prolegomena, ed. John Bolt, trans. John Vriend (Baker Academic, 2003), pp. 608-9.