Spinoza's theology, although original, owes much to the cultural soil that nourished it. His parents were among the many “Marranos” - Portuguese Jews who in their native country had been compelled outwardly to embrace Roman Catholicism - who had emigrated to Amsterdam in the early seventeenth century. In the freedom of their new country, the immigrant Marrano community set out to recover its full religious heritage, and to shed beliefs and practices contrary to it. However, some of its members, of whom Spinoza was one, not only remained attached to non-Jewish elements in their Marrano culture, but, having embraced the revolution in the physical sciences associated with Galileo, Bacon, and Descartes, wished to pursue its implications for religion. When he was twenty-three, partly because he would not renounce these non-Jewish interests, the Amsterdam synagogue expelled and cursed him. Yet even among the radical Christians who befriended him, and who repudiated the Trinitarian and Christological doctrines he found absurd, only a small circle of intimates were prepared to follow him when he jettisoned the conception of God as a supernatural creator of the natural universe, and developed a “naturalized” theology, in which the natural universe, as conceived in Baconian-Cartesian natural science, derives its existence from nothing above and beyond it.

Sidgwick's Methods of Ethics appears to defend a revised utilitarianism against both egoism and intuitionism, while conceding that the practical results of enlightened egoism largely coincide with those of utilitarianism, and that the utilitarian greatest-happiness principle can be justified only as a fundamental intuition. It is true that Sidgwick was distressed by the description of his treatment of intuitional morality as “mere hostile criticism from the outside” and protested that that morality “is my own… as much as it is any man's; it is, as I say, the ‘Morality of Common Sense,’ which I only attempt to represent so far as I share it” (ME, x). However, he could not well have denied that, in The Methods of Ethics, the endorsement tentatively accorded to intuitional morality as a system is in the end withdrawn. Ultimately it is concluded that utilitarianism can define and correct what intuitional morality is vague or mistaken about, and can complete what common sense does not venture to treat at all. Hence the teaching of The Methods of Ethics appears to be that, at the final stage of moral thinking, utilitarianism replaces intuitional morality, even though it incorporates, on a new basis, many intuitional precepts.

Yet, closer reading of Sidgwick's ethical writings throws doubt both on whether he was consistent in reaching these conclusions and on whether he held them firmly.

Philosophical and theological motivations for Aquinas' work

At least two distinct purposes may be discerned in Aquinas' various writings on human action. One is to complete and correct Aristotle's treatment of it in the Nicomachean Ethics, to which he of course pays close and respectful attention. A second springs from his primary commitment to theology. Reflecting on what is said in the Scriptures and the writings of the Fathers about such topics as the fall of Adam, sin, conversion, and the operation of grace, theologians produced a body of doctrine about various aspects of human acts. To Aquinas' mind, this teaching settles certain questions authoritatively: as when it declares that voluntary human acts are commanded by their agents freely, and not by necessity. In addition it introduces certain concepts into the theory of action, for example, those of enjoyment and consent. Aquinas undertakes to incorporate these contributions of theology, where sound, into a revised Aristotelian theory.

Aristotelian causal theories

Aristotelian theories of action are causal, and causal in a distinctive way. To do something, to perform an act, is to cause something. And causing something is always to be investigated in terms of a pair of fundamental concepts, dynamis and energeia, which appear in Thomas' Latin as potentia (potency) and actus (act). The power or capacity of an object to cause something – whether a change of state, or a persistence in a state – largely determines what that object is. Brute animals are distinguished by their possession of powers of sensation and bodily movement.