Natural law

Synderesis

The fundamental obligation imposed on us by right reason is to "do good and avoid evil."

This basic principle cannot be derived from any higher principle.

It cannot be "proved" by formal proof based on axioms of logic. It is something taken for granted in and by logic. We ought to accept the conclusions of logic, where they apply, because this is the good of the mind (to know the difference between what is true and false). Without the assumption of synderesis, logical reasoning has no force.

Those who deny that we ought to do good and avoid evil can form their denial only by appealing to it. They say, "You ought not to believe that people ought to do good and avoid evil; it is evil (wrong) for you to hold that view." This is a self-referentially inconsistent position; it is a form of hypocrisy to say one thing ("People cannot be obliged to do good and avoid evil") and do another (describe a standard by which the listener is obliged to do good and avoid evil).

Deontology

I believe that ethicists classify the natural-law approach of Catholicism as "deontological."

Online Etymology Dictionary

science of moral duty, 1826, from Gk. deont-, comb. form of deon "that which is binding, duty," neut. prp. of dei "is binding;" + -logia "discourse" (see -logy). Said to have been coined by Bentham.

Natural and unnatural rights

I have the feeling that there is something peculiar happening in our jurisprudence. On the one hand, natural law is set aside on the basis of "what most people want." On the other hand, an appeal to some kind of objective moral order is implicit in the judicial decisions like those that weaken DOMA or Proposition 8--some "higher law" than the law makes such efforts "unconstitutional." It's baffling. The courts are "seeing things" in the law that are not on the surface. "Manufactured rights"--hand-made, just for you. Right to same-sex marriage, right to abortion, right to privacy among consenting adults, right to kill the handicapped, right to die. But there is no right to free speech to oppose these measures; that is evidently a hate-crime.