I do not mean that these axiomatic truths are cognisable by all. For the apprehension of them, as for the apprehension of simpler axioms, a certain mental growth and a certain mental discipline are needed. In the _Treatise on Natural Philosophy_ by Professors Thomson and Tait [1st ed.], {221} it is remarked that “physical axioms are axiomatic to those only who have sufficient knowledge of the action of physical causes to enable them to see at once their necessary truth.” Doubtless a fact and a significant fact. A plough-boy cannot form a conception of the axiom that action and reaction are equal and opposite. In the first place he lacks a sufficiently generalized idea of action—has not united into one conception pushing and pulling, the blow of a fist, the recoil of a gun, and the attraction of a planet. Still less has he any generalized idea of reaction. And even had he these two ideas, it is probable that, defective in power of representation as he is, he would fail to recognize the necessary equality. Similarly with these _a priori_ ethical truths. If a member of that Fijian slave-tribe who regarded themselves as food for the chiefs had suggested that there might arrive a time when men would not eat one another, his implied belief that men might come to have a little respect for one another’s lives, condemned as utterly without justification in experience, would be considered as fit only for a wild speculator. Facts furnished by every-day observation make it clear to the Biluchi, keeping watch in his mud-tower, that possession of property can be maintained only by force; and it is most likely to him scarcely conceivable that there exist limits which, if mutually recognized, may exclude aggressions, and make it needless to mount guard over fields: only an absurd idealist (supposing such a thing known to him) would suggest the possibility. And so even of our own ancestors in feudal times, it may be concluded that, constantly going about armed and often taking refuge in strongholds, the thought of a peaceful social state would have seemed ridiculous; and the belief that there might be a recognized equality among men’s claims to pursue the objects of life, and a consequent desistence from aggressions, would have been scarcely conceivable. But now that an orderly social state has been maintained for generations—now that in daily {222} intercourse men rarely use violence, commonly pay what they owe, and in most cases respect the claims of the weak as well as those of the strong—now that they are brought up with the idea that all men are equal before the law, and daily see judicial decisions turning upon the question whether one citizen has or has not infringed upon the equal rights of another; there exist in the general mind materials for forming the conception of a _régime_ in which men’s activities are mutually limited, and in which maintenance of harmony depends on respect for the limits.