Children learn the fundamental principles of natural law at a very early age.

Children learn the fundamental principles of natural law at a very early age.  Thus they very early understand that one child must not, without just cause, strike or otherwise hurt, another; that one child must not assume any arbitrary control or domination over another; that one child must not, either by force, deceit, or stealth, obtain possession of anything that belongs to another; that if one child commits any of these wrongs against another, it is not only the right of the injured child to resist, and, if need be, punish the wrongdoer, and compel him to make reparation, but that it is also the right, and the moral duty, of all other children, and all other persons, to assist the injured party in defending his rights, and redressing his wrongs.  These are fundamental principles of natural law, which govern the most important transactions of man with man.  Yet children learn them earlier than they learn that three and three are six, or five and five ten.  Their childish plays, even, could not be carried on without a constant regard to them; and it is equally impossible for persons of any age to live together in peace on any other conditions.

It would be no extravagance to say that, in most cases, if not in all, mankind at large, young and old, learn this natural law long before they have learned the meanings of the words by which we describe it.  In truth, it would be impossible to make them understand the real meanings of the words, if they did not understand the nature of the thing itself.  To make them understand the meanings of the words justice and injustice before knowing the nature of the things themselves, would be as impossible as it would be to make them understand the meanings of the words heat and cold, wet and dry, light and darkness, white and black, one and two, before knowing the nature of the things themselves.  Men necessarily must know sentiments and ideas, no less than material things, before they can know the meanings of the words by which we describe them.

Lysander Spooner