"It is sometimes urged against political, as against ethical, theory that it is incapable of giving definite answers; for instance, it is said that if you hold some view strongly about the nature of liberty or the rights of the individual or the spiritual value of democracy you cannot prove your position to an opponent with the same finality with which you can prove a proposition in geometry. This is perfectly true, and this is one very good reason for avoiding the term 'political science.' Science, rightly or wrongly, is a term usually applied to spheres of knowledge where exact results are obtainable, as in mathematics, and thus the use of the phrase 'moral and political science' is open to serious misconception.
Admittedly in ethics and politics you cannot, in the last resort, prove your opponent to be wrong; if he likes to maintain that selfishness is plain common sense, that ordinary morality is conventional humbug, and that right is might in all forms of society you cannot demonstrate his error as you can show up the fallacy of one who believes equilateral triangles to have unequal angles. The difference is this. Geometry lays down a series of postulates and axioms, about which there is a general concordance of opinion ; from these it works straight forward to certain, demonstrable results. But in ethics and politics there may be a fundamental disagreement about first principles, since one man's virtue is another man's vice. These first principles cannot be proved, but are the result of a direct intellectual judgment or a mere emotional intuition.
But that is no reason for abandoning as useless all study of ethical and political theory. What these studies can achieve is to bring men together in a common field of reflection and discussion, and, when this has been done, something fruitful has been accomplished. They begin to define their terms and to understand each other's standpoint; they may not in the end agree, nor is it desirable that all men should always agree. That it takes all sorts to make a world is both true and happily true.
What we have to avoid is unnecessary misunderstanding. The Tory Imperialist and the International Socialist will never lie down in intellectual amity, nor will one ever prove the other to be wrong. But large numbers of men who disagree will, by studying the opinions of others and the history of those opinions, realise where, how, and why they disagree. Thus the resulting contest, instead of being a blind, happy-go-lucky struggle on the lines of catch-as-catch-can, will become orderly and purposive, conducted according to some sensible rules of the ring. And if the result is not unity but a mutual respect and toleration, the study of moral and political theory is more than justified."
(Ivor Brown, English Political Theory )