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St. Thomas Aquinas was the greatest medieval philosopher. He tried to show the harmony between faith and reason, and between Christianity and philosophy. Aquinas's views have been very influential, especially in Catholic thought.

These summaries and problems deal with Aquinas's Summa Theologica: questions 91 (articles 2 and 4) and 94 (articles 2, 4, and 5) of part I-II (Prima Secundae). These summaries and problems are copyrighted (c) 1998 by Harry J. Gensler but may be distributed freely.

Law in general

Aquinas uses the term "natural law" to refer to morality, or the moral law. He sees law as a rational attempt to guide action. A law is a prescription that we act or not act; it may also exist in us as an inclination to act in certain ways. A law must be made and promulgated by those in charge of the community.

Laws must be directed to the common good -- to the happiness that is the goal of human actions. Prescriptions that aren't for the common good are unjust. A so-called "unjust law" isn't properly a "law" at all.

"Happiness" in Aquinas refers both to (1) temporal happiness (living a good life on earth), and (2) supernatural happiness (eternal happiness with God in heaven). Our final goal is happiness in both senses, but particularly the second.

There are four kinds of law

    1. Eternal law. God governs the universe through physical laws, moral laws, and revealed religious laws. Eternal law includes all of these.

    2. Natural law (moral law). This is the part of the eternal law that applies to human choices and can be known by our natural reason.

    3. Human law (civil law). We create our own laws, in order to apply the natural law to the specific circumstances of our society.

    4. Divine law (biblical law). In the Bible, God reveals a special law to guide us to our supernatural end of eternal happiness with Him.

First principles

The first principles of natural law are self-evident truths. In this they resemble the first principles of speculative reason (such as the law of noncontradiction).

Law requires that we act in accord with reason. The first principles of the natural law are "Good is what all things seek after" and "Good is to be done and promoted, and evil is to be avoided." So whatever practical reason naturally apprehends as our good (or evil) is to be done (or avoided).

The first principles of the natural law are the same for everyone and are known to all; these principles cannot change and cannot be abolished from the human heart. The secondary (derivative) principles depend on circumstances and can change. They are less certain, and often are not known to all. Human and divine law can add to these secondary principles.

Aquinas's style

Aquinas followed a special pattern in his writing. He gives a question ("Is there a God?"), then objections to his own view ("It seems that there is no God, because..."), then an inspiring quotation ("On the contrary, the Bible says..."), then his answer ("I answer that, God's existence can be proved in five ways..."), and finally his response to the initial objections.

Web resources

Click below to read Aquinas's writings (see especially articles 2 and 4 of question 91 and articles 2, 4, and 5 of question 94) or an article about Aquinas:

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This set has 22 problems.