Thomas D. D’Andrea, "The Natural Law Theory of Thomas Aquinas," Natural Law, Natural Rights, and American Constitutionalism -- a project of the Witherspoon Institute.

Thomas D. D’Andrea considers Aquinas’ theory of natural law at the Witherspoon Institute’s Natural Law, Natural Rights, and American Constitutionalism site.

Excerpt:

Thomas Aquinas is generally regarded as the West’s pre-eminent theorist of the natural law, critically inheriting the main traditions of natural law or quasi–natural law thinking in the ancient world (including the Platonic, and particularly Aristotelian and Stoic traditions) and bringing elements from these traditions into systematic relation in the framework of a metaphysics of creation and divine providence. His theory sets the terms of debate for subsequent natural law theorizing.

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Natural Law, Natural Rights, and American Constitutionalism