Rudi Te Velde says that Aquinas did not write the Summa contra Gentiles as a missionary manual for Dominicans to evangelize the Muslims. This timeless work was written to refute certain errors that had come to light in the Medieval context. These errors go beyond that of the Muslim faith.
The list of errors is not restricted to contemporary thought. The errors are attributed to the ancient natural philosophers, to the “Platonists,” to Avicenna and Averroes (they are not in all respects trustworthy guides in interpreting Aristotle), to heretics like Origen and the Manichees, but most of all simply to “quidam,” to anonymous teachers who hold a more or less reasonable opinion, based on philosophical principles, that conflicts with the truth of Christian faith. (Te Velde, “Natural Reason in the Summa Contra Gentiles” in Brian Davies, ed. Thomas Aquinas: Contemporary Philosophical Perspectives, p. 127)
Aquinas must be seen in his context. The Christian world had known the philosophy of the Neo-Platonists since the very beginning but the Medieval world experienced a rebirth of Aristotle, who was being introduced and interpreted mainly by Muslim and Jewish authors. Aristotle’s non-Christian interpreters were leading Medieval teachers at the University of Paris and elsewhere astray with their extreme synthesis. Therefore, Aquinas saw it as his goal to rescue Aristotle from the extremists and preserve the Christian faith, all in the name of Truth. Te Velde also affirms that Aquinas did not present arguments based on pure reason divorced from Christian Truth. He was doing the opposite – basing his arguments for truth on the first principles claimed by his opponents:
Aquinas’s strategy is to discuss and combat the claims in the light of reason’s own criteria and rules learned from the philosophi themselves. Insofar as faith requires not only confession but also reflection and understanding in order to be a human faith, Aquinas shows the believer how ‘philosophical’ reason can be assimilated if only reason is brought to correct its errors and false pretensions and becomes aware of its human point of view in relation to the truth of faith. (Ibid)
The contra Gentiles was therefore written for Christians to consider the arguments of the philosophi and their contradictions, not only with the claims of Sacra Pagina but with those philosophi’s own first principles of knowledge. That’s not all either. Aquinas aimed to demonstrate the foolishness of relying solely on natural reason as a foundation for claims at Truth. Te Velde continues:
A reason that cannot tolerate our being asked to hold something on faith represents a veritable Trojan horse for the Christian community. If reason were justified in its claim to autonomy, the only way Christianity could affirm its faith would be by rejecting reason, by excluding rational reflection based on philosophy. Aquinas chooses not to go along that way. It is his conviction that natural reason can be integrated in the Christian consciousness of truth, but not unless reason gives up its claim to autonomy and acknowledges its human condition in knowing the truth [emphasis added]. Not reason as such, but the presumption of reason to have an absolute hold on truth prevents a reasonable understanding of the truth of faith. So the issue is not a defense of the ‘reasonableness’ of Christian faith before reason. Aquinas’s objective is to confirm natural reason with its own condition, to make reason aware of its limitations in order to prevent reason from unreflectively imposing its own limits on the search for truth. We need more truth than our reason can grasp. (Ibid., p. 129)
So, contrary to what Evangelical Christians often assume about Aquinas his was actually an argument against autonomy. The contra Gentiles was not written to atheists nor to anyone outside the Christian community. It was written to Christians as a guide for the perplexed in order to answer the “new” philosophical arguments that seemed to contradict Christian tradition and faith. In the end Aquinas’s answer to the gentiles was based on the authority of scripture, pointing out the absurdity of claiming absolute Truth and certainty from an autonomous appeal to the human intellect.