St. Thomas Aquinas's Core Philosophical Doctrines

St. Thomas Aquinas: Theory of Knowledge

St. Thomas Aquinas's Theory of Knowledge explains intellectual knowledge through the theory of abstraction. Drawing essentially from Aristotle, Aquinas posits that the agent intellect abstracts (i.e., separates, though not physically) the intelligible (universal) from the individual sensible images (particulars). This abstracted universal is then presented to the patient intellect, enabling it to know the act of knowing. This process leads to the understanding of concepts through the essences of things. The attribution of one concept to another results in a judgment, which is true if what it asserts corresponds to reality.

St. Thomas Aquinas: Ethical Philosophy

In Ethics, St. Thomas Aquinas adopts Aristotle's doctrine of happiness as the ultimate goal, emphasizing the role of right reason and the division of moral and intellectual virtues. However, for Aquinas, the ultimate goal is transcendent: the beatific vision of God. Furthermore, the moral life is elevated by grace to holiness. A significant innovation in Aquinas's ethics is his conception of law. Just as there are supreme theoretical principles (such as the principle of non-contradiction), there are also supreme moral principles, embodied in the "right reason" that forms the core of conscience. The primary principle is: "We must do good and avoid evil." These principles are the expression of Natural Law, a human understanding of the Eternal Law.

St. Thomas Aquinas: Political Philosophy

Regarding Political Philosophy, St. Thomas Aquinas asserts that positive law (i.e., the specific laws governing a given society) must align with Natural Law, whose ultimate reference point is the Eternal Law, divinely revealed. Positive law is defined as an ordinance of reason for the common good. The common good is not merely the sum of individual goods, but rather the good of individuals as they are open to the fulfillment of a project that benefits everyone. Achieving this common good requires that human actions are governed by justice, peace within the State, and the meeting of basic life needs. The State government is instituted to ensure these conditions necessary for the common good.

In terms of concrete political organization, since it is not easy to find the perfect individual to serve as king, Aquinas suggests that the best form of government is a mixed combination of monarchy, aristocracy, and democracy. Aquinas believes that the State has autonomy within its own sphere, but should be subordinate to the Church regarding supernatural life. He is thus an advocate of what is known as the indirect power theory of the Church over the State.