Natural law

Here is as good a nutshell explanation of natural law as you are likely to find:

Once again, let me emphasize that the natural law is not a specifically Catholic thing. Astonishingly, each time I have mentioned the natural law, some have insisted that it is unfair to expect others to conform to Catholic doctrine! Truly, the mind boggles, for the whole point of the natural law is that it is universal and, well, natural. The critic’s very appeal to lack of fairness is in fact an appeal to the natural law. All rational moral argument appeals to the natural law, even when it erroneously uses one part of the natural law against another. Confusion, passion and self-interest may at times cause us to make mistakes in interpreting and applying the natural law, but the inescapable fact remains that the natural law is the only way we have of knowing when the positive law is immoral. Without it, there can be no concept of “right” apart from the concept of “power”.

Thanks to Dr. Jeff Mirus from CatholicCulture.org