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How did Thomas Aquinas connect law with the common good?
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Philosophy of law
Plato, marble portrait bust copied from an original of the 4th century bce; in the Capitoline Museums, Rome.
St. Thomas Aquinas defined law as an "ordinance of reason," asserting that its fundamental purpose is to serve the common good of the political community.1
For Aquinas, law functions as a coordinated plan that enables a society to achieve tangible and intangible goods that individuals could not realize on their own. He connected this purpose to the validity of law through two primary mechanisms:1
- Direct Deduction: Legal rules may directly correspond to objective moral principles, such as the prohibition of homicide derived from the moral wrongness of murder.1
- Determinatio: Lawmakers specify how general moral principles apply to specific circumstances to facilitate social coordination. For example, while morality does not dictate which side of the road to drive on, a law requiring a specific side is binding because it serves the moral necessity of preventing harm and facilitating commerce.1
Aquinas maintained that if a law is not derived from valid moral principles in these ways, it is "unjust" and lacks binding authority. Consequently, he argued that legitimate political authorities must be motivated by the "care of the community," as laws created from other motivations fail to serve the common good and are inherently unjust.1