For another illustration of the same principle, we may take *the relation between parents and children*. In the ruder stages of society, and especially among a nomadic or migratory people, there is not a sufficient knowledge of the resources of nature or the possibilities of art, to render even healthy and vigorous life more than tolerable; while for the infirm and feeble, life is but a protracted burden and weariness. At the same time, there is no apprehension of the intellectual and moral worth of human life, still less, of the value even of its most painful experiences as a discipline of everlasting benefit. In fine, life is little more than a mere struggle for existence. What wonder then, that in some tribes filial piety has been wont to relieve superannuated parents from an existence devoid equally of joy and of hope; and that in others parental love may have even dictated the exposure—with a view to their perishing—of feeble, sickly, and deformed children, incapable of being nurtured into self-sustaining and self-depending life? But increased conversance with nature and art constantly reveals new capacities of comfort and happiness in life, and that, not for the strong alone, but for the feeble, the suffering, the helpless, so that there are none to whom humanity knows not how to render continued life desirable. At the same time, a higher culture has made it manifest that the frailest body may be the seat of the loftiest mental activity, moral excellence, and spiritual aspiration, and that in such a body there is often only a surer and more finished education for a higher state of being. Filial piety and parental love, therefore, do all in their power to prolong the flickering existence of the age-worn and decrepit, and to cherish with tender care the life which seems born but to die. There is, then, to the limited view of the savage, an apparent fitness in practices which in their first aspect seem crimes against nature; while increased knowledge develops a real and essential fitness, in all the refinements and endearments of the most persevering and skilful love. These examples, which might be multiplied indefinitely, show *the dependence of conscience on knowledge*, not for relatively right decisions, but for verdicts in accordance with the absolute right. There is no subject that can be presented for the action of conscience, on which, upon precisely the same principles, divergent and often opposite courses of conduct may not be dictated by more or less accurate knowledge of the subject and its relations.