I have enjoyed reading “Mere Christianity” because of the way it connects the Law of Nature to the existence of a Power in the universe. (Naturally as a Christian I believe this Power to be God) I have always been convinced of the existence of a Law of Nature mainly due to the fact that I have often been compelled to act in ways that I did not prefer to act. So, while I did not need to be convinced of the Law of Nature I value the arguments that Lewis has laid down which support my own beliefs on this matter.
To begin Lewis asserts that it is the Law of Nature to which many of man’s daily arguments appeal. Often the only justification offered in an argument is that one way is fair while the other is not. This sense of fairness is a sign of the Law of Nature—both parties are expected to understand the definition of fairness and come to the same conclusion while looking at the issue in light of it. Granted within different cultures these definitions may vary slightly but these differences are generally inconsequential. Lewis also shows how even those who claim that no Law of Nature exists will appeal to it when they are being acted upon unjustly or indecently. Lewis then shows how people can choose to disobey the Law of Nature and often do. However, when a man acts in a manner counter to the Law of Nature he feels compelled to make excuses for his behavior.
The second chapter shows that the Law of Nature is more than an instinct. The Law of Nature judges and directs our instincts in much the same that a sheet of music judges and directs which keys a pianist strikes. (I find this piano analogy very clear and helpful in this argument) When faced with two different actions led by two different instincts it is not always the more powerful instinct that the man follows, thus there must be something else occurring within the man to make him chose the lesser instinct. Some people contend that the Natural Law is merely a social order that is ingrained in man from childhood. Lewis believes that while the Natural Law is taught to man from childhood it was not invented by man. One reason for this belief is that a very similar Natural Law exists in every culture. It would be quite coincidental for every culture to have invented such a similar Natural Law without having some common guidance. A second reason is that when two opinions on the Natural Law are presented to a man he can determine which is “better” or “truer.” Lewis says that our understanding of the moral law has changed for the better. This belief explains why man prefers “civilized morality to savage morality, or Christian morality to Nazi morality.”
Lewis then shows how the Natural Law is actually beyond the reality we are most familiar with. Lewis contends that the Natural Law is what man ought to do and not necessarily what he does. This means that the Natural Law cannot be observed by an outsider looking at the facts of man. There is no explanation for why a man sometimes views things that are inconvenient for him as good and sometimes as bad or why he occasionally behaves in a way that is counter to his own desires. Lewis then follows a very complex argument for why this idea of a Natural Law cannot be gotten rid of. Basically Lewis shows how it is impossible to logically understand the actions that are caused by the Natural Law. Through all this Lewis comes to the conclusion that there is a reality beyond what we usually interpret as reality.
The final portion of this reading is an argument verifying the acceptance of our personal observations of this second reality. This is a very difficult logic to explain without following it as Lewis presents it. Lewis concludes that the power that exists behind the Law of Nature “would be not one of the observed facts (of man) but a reality which makes them.” He goes on to say that “the only way in we could expect to it [the power] to show itself would be inside ourselves as an influence or a command trying to get us to behave in a certain way.” As the previous arguments have concluded such a power does exists for man and thus it can be assumed that such a power also exists in other areas of nature.
I have attempted to explain this very complicated but logical argument and I suggest that if this explanation does not satisfy you then you should read Lewis’ “Mere Christianity”. Lewis has writtin a logical argument to explain the existance which is obvious to most people, of a Natural, Moral Law.