(1) Contrary to Strauss's claim that Aquinas takes the side of revelation against reason and thus denies the classic teaching of natural right, West argues that Aquinas understands the conflict between reason and revelation, and that he adapts the teaching of classic natural right to the circumstances of medieval Christianity.
From the very beginning of the section of the Summa Theologica on faith, Aquinas draws a sharp contrast between faith as belief in things unseen and reason or science as demonstrative knowledge of things seen (II-II, q. 1, aa. 4-5). This corresponds closely to Strauss's account of the reason-revelation debate. Scientific knowledge comes from what human beings can see and know by natural reason and natural experience. By contrast, matters of faith depend on the authority of scripture, on what we hear from others rather than what we can see for ourselves.
Aquinas declares: "The reasons employed by holy men to prove things that are of faith are not demonstrations; they are either persuasive arguments showing that what is proposed to our faith is not impossible, or else they are proofs drawn from the principles of faith, i.e., from the authority of sacred scripture" (II-II, q. 1, a. 5, ad 2).
That Aquinas understands natural law as depending on human reason but not divine revelation should be clear from the famous passage in which he lays out the levels of the natural inclinations of human beings that are naturally apprehended by reason as being good (I-II, q. 94, a. 2). In this passage, there are no Biblical citations or appeals to divine revelation. There are four kinds of natural inclinations--self-preservation, the sexual generation and rearing of offspring, living in society, and knowing the truth about God. The natural inclination to know the truth about God supports the natural law precept to "shun ignorance." Even here there is no reference to revelation, thus suggesting that this could be the purely philosophic quest to ascend to the first causes of all things through natural reason alone, which would move towards "the highest cause of the whole universe, namely God" (I, q. 1, a. 6). As guided by natural law, human beings answer the question of what God is by natural reason alone.
West sees Aquinas as arguing that God creates two independent paths to guide human beings--natural law as the path of human nature and natural reason and divine law as the path of divine revelation and supernatural faith. By separating these two paths, Aquinas can separate human law and government from the authority of the Church. Human law is derived only from natural law, not divine law. Human law is concerned with religion only in so far as religion promotes the moral order of society (I-II, q. 91, a. 3; q. 98, a. 1; q. 99, a. 3). Priests serve the common good of the people by praying to God for the people, but princes serve the common good by governing the people (I-II, q. 95, a. 4). The clergy have the authority to interfere in secular politics only to prevent tyrants from commanding their subjects to perform idolatrous rituals (I-II, q. 96, a. 4; II-II, q. 60, a. 6, ad 3). Thus, Aquinas argues for a qualified separation of church and state.
It might seem that the natural law is a positive divine law in so far as the natural law is said to be part of the eternal law of God. But West argues that Aquinas identifies the eternal law as the unchanging mind of God--the reason or principle of divine providence--as manifest in the eternal order of nature. Consequently, human beings obey divine providence by obeying the order of nature (I-II, q. 93, a. 5).
West asks (p. 87): "Was Aquinas living 'in a community governed by divine law,' merely pretending to believe in that law, when in fact he was adjusting natural right 'to the belief in the existence of divinely revealed law'? Was he pretending to be a political theologian while in fact being a political philosopher? Was the great saint nothing more than a philosopher dressed up in priestly robes?" West suggests the answer in each case is yes. One must consider the possibility that "in the end Aquinas covertly but firmly took the side of reason over revelation" (86).
To see this, however, we must see that Aquinas is engaging in secret writing--that the exoteric teaching for most readers who see only the surface of the writing differs from the esoteric teaching for the few readers who see beneath the surface. Following the lead of Strauss's Persecution and the Art of Writing, West argues that Aquinas had to worry about being persecuted for his Aristotelianism, which was a fact of life at the University of Paris, and he had learned from Moses Maimonides the importance of secret writing in such circumstances.
In fact, Aquinas says in the Prologue to the Summa Theologica that this is book for instructing beginners who need "milk to drink, not meat." Moreover, he argues--like Maimonides--that sacred scripture uses metaphorical language to hide the truth from vulgar readers while revealing it to the few thoughtful readers (ST I, q. 1, a. 9; q. 68, a. 3; I-II, q. 98, a. 3, ad 2; II-II, q. 40, a. 3).
Moreover, when Aquinas examines sacred doctrines, he always tries to interpret them in such way as to render them rationally comprehensible to natural reason, which suggests that human reason is the standard by which divine revelation is to be judged. In those cases where Aquinas cannot interpret a doctrine as reasonable--as, for example, with the doctrine of original sin or the belief in miracles--he contradicts himself in ways that point to the problem, and he indicates that he must answer "according to the Catholic faith," and thus suggests that he cannot openly question the Church's authority (I-II, q. 81, aa. 1-3; II-II, q. 154, a. 2, ad 2; q. 104, a. 4, ad 2; Summa Contra Gentiles, bk. 3, chs. 100-101).
(2) To Strauss's second objection--that Aquinas's natural law is inflexible and thus leaves no room for prudence--West replies that Aquinas actually allows for flexibility and prudence. In applying general principles to the contingent circumstances of action, practical reason must have a wide latitude for judgment (I-II, q. 94, aa. 4-6). Although Aquinas does say that the general principles of natural law are unchangeable, these general principles are very few, and they seem to be reducible to the vague idea that "good is to be done and promoted, and evil is to be avoided," which seems to correspond to Aristotle's teaching that all human actions aim at the good (I-II, q. 94, a. 2).
Moreover, even with respect to the apparently fixed principles of the Decalogue--such as the prohibitions against lying and stealing--Aquinas allows for variation in exceptional circumstances where public safety or individual need require it (II-II, q. 66, a. 7; q. 110, aa. 1-4). "Necessity knows no law" (I-II, q. 96, a. 6).
West also argues that the flexibility of Aquinas's natural law teaching extends even to divorce and birth control. Aquinas indicates that while divorce in the Old Testament was "against the principle of a sacrament," it was not against nature (I-II, q. 102, a. 5, ad 3). Marriage as a sacrament of the Church is a matter of divine revelation, and this does not allow for divorce. But marriage as rooted in natural inclinations might allow for divorce in exceptional circumstances.
Aquinas teaches that "against the good of man is every emission of semen in such a way that generation cannot follow" (Summa Contra Gentiles, bk. 3, ch. 122). The Catholic Church has interpreted this to prohibit any form of birth control other than "Natural Family Planning" (NFP). But West argues that this does not follow from Aquinas's standard, because no method of birth control is so completely effective that "generation cannot follow." In fact, NFP is actually more effective than most other forms of birth control in preventing conception.
Furthermore, West argues, in the circumstances of the modern Western world, where the death of infants and children has become rare, birth control actually promotes the ends of family life, because it allows parents to insure that they not have more children than they can possibly rear and educate.
West concludes that the Catholic Church's condemnation of artificial birth control cannot be supported by Thomistic natural law.
(3) West denies Strauss's assertion that Aquinas sees a "basic harmony between natural right and civil society." In fact, Aquinas clearly states that there is a disproportion between natural law and civil society. "Human law does not prohibit everything that is forbidden by the natural law." This must be so because
Human law is framed for a number of human beings, the majority of whom are not perfect in virtue. Wherefore human laws do not forbid all vices, form which the virtuous abstain, but only the more grievous vices, from which it is possible for the majority to abstain; and chiefly those that are to the hurt of others, without the prohibition of which human society could not be maintained: thus human law prohibits murder, theft, and such like. (I-II, q. 96, a. 2)
West sees this as pointing towards the modern Hobbesian and Lockean teaching that government should be largely limited to protecting life, liberty, and property.
(4) Contrary to Strauss's claim that Aquinas's doctrine of synderesis or conscience is an unreasonable conclusion from his belief in divine revelation, West argues that conscience for Aquinas is nothing but the human mind's grasping of the natural inclinations as good. First the mind must apprehend these natural inclinations as setting the ends of action, then prudence judges the best means for achieving these ends (I, q. 79; II-II, q. 47, a. 6).
Moreover, it is not true, as Strauss says, that this teaches the universal promulgation of natural law equally to all human beings. Some human beings are more prudent than others, and thus human judgment is fallible (I-II, q. 94, a. 4; II-II, q. 47, a. 5).