C.I. Lewis, the well-known 20th century American philosopher from Harvard notes in his book The Ground and Nature of the Right that the concept of obligation pervades all of human thinking. Obligation does not refer only to Moral behavior – it applies to every aspect of thinking and behavior that can called right as opposed to wrong. There is a right and wrong way to calculate numbers. There is a right and a wrong way to ride a horse. There is a right way and wrong way to drive a car and so on. It is only when we come into the sphere of social activity between man and man that we then can invoke the moral aspect of obligation
As pointed out by Lewis Carroll in the dialogue between Achilles and the Tortoise , we see that even basic logical processes require our assent – to say,” yes, that is correct, I accept that.” Accompanying this assent is a feeling of obligation – that I must say “yes”, that I must agree. When we enter the area of obligation, we are already in the area of the heart – we are asking for commitment and assent. This does not mean that statements of obligation are meaningless, as C.L. Stevenson would have had us believe. But there is an emotive element which provides the incentive for commitment to truth.
If the other side refuses to accept the dictates of logic or the sense of right and wrong, both in common human endeavors or in ethical and human relationships, so then dialogue ceases. This is what we mean by rationality; accept the norms of basic logic and basic human behaviour. If the other side has an agenda that negates these assumptions, such as the commitment to Communism (the Totalitarianism of Lenin and Stalin), the commitment to Nazi Ideology, the commitment to Radical Islamism, then there is a negation of rationality and common human decency, the basic norms accepted by the West (accepted at least in theory). The other side is saying “I will obliterate you” and “we will act on this rule.” (The interesting historical question is how Soviet Russia was held at bay throughout the Cold War). The fault of the West today is the willingness to ignore these basic rules governing the behaviour of nations and their significance to International Relations.
Within Judaism, the commitment to obey both the Seven Mitzvot of B’nai Noach and the Ten Commandments, constitute the foundation of civilization and progress. Hence with Amalek, who fit these criteria of a destructive and totalitarian society, the commandment was to obliterate them. There was no other rational choice.