The plastic power by which men accommodate their actions and even their maxims of conduct to modifications in surrounding circumstances is one of the advantages which they gain by the progress of civilisation.  In ancient society the tyranny of custom is often almost absolute.  In modern society changes, which would otherwise require the drastic hand of the reformer, are often quietly effected by the gradual and almost imperceptible action of the people themselves.  It is thus that the equity branch of English law, and much of our case law, grew up, giving expression to changes which had already occurred in the current of popular opinion.  It is thus that the obligation of ‘gentlemen’ to offer, on the slightest provocation, and to accept, without questioning, a ‘challenge’ to take each other’s lives, has, in most civilized countries, now grown obsolete, having gradually become enfeebled together with the exaggerated military spirit which gave it birth.  It is thus also that, with an increase of the industrial spirit, with softened manners, and with that quickening of our sympathetic nature which has gradually been effected by the teaching of Christianity, a strong sentiment against slavery, a respect for human life as such, a regard for the weak, the suffering, the oppressed, and many tender feelings of a similar kind, have almost insensibly been developed as an essential element in modern civilisation.

These considerations naturally lead me to notice the two different ways in which the test of conduct may be, and as a fact is, applied.  One mode is the conscious and intentional application of it by the reflective man.  The other is the semi-conscious and almost instinctive application of it by the community at large.  In morals, as in the arts, men, almost without knowing it, are constantly re-adjusting their means to their ends, feeling their way to some tentative solution of a new difficulty or a better solution of an old one, shaping their conduct with reference to the special needs of the situation in which they are placed.  It is thus, for the most part, that new circumstances develope new rules, and that the simple maxims of a primitive people are gradually replaced by the multifarious code of law and morals with which we are now familiar.  The guiding principle throughout the process is the conception of their own good, comprehending, as it does, not only ease, personal comfort, and gratification of the various appetites and desires, which, in the early stages of society, are the preponderating considerations, but also those higher constituents of welfare, both individual and social, which attain an ever-increasing importance as society advances, such as are the development of the moral, the intellectual, and the aesthetic faculties; the purification of the religious sentiments, the expansion of the sympathetic feelings, the diffusion of liberty and prosperity, the consolidation of national unity, the elevation of human life.  This principle