This oration cannot have the merit of an original study. Had I the equipment I have not the leisure to carry my investigations to the sources. Yet I may have attained to some maturity of judgment herein by long occupation of my mind since, in 1863, my old friend Mr Thomas Marshall of Leeds, sometime of St John’s College, Oxford, interested me in the life and work of Roger Bacon, the only eminent forerunner of the great naturalists of the seventeenth century. The art of the Middle Ages and the social and political history of the time have fascinated modern Europe; for medieval thought, though its phrases survive in their mouths, few persons have shown any care: yet to these conflicts we owe what we are. No great battles of mankind have been fought in vain; none of its great captains has deserved oblivion. Yet we shrug our shoulders at their uncouth or outlandish names; we assume that from their chairs there issued naught but rhetoric, casuistries and fallacies, and that their multitudinous disciples were silly moths. Each period of human achievement has its phases of spring, culmination, and decline; and it is in its decline that the leafless tree comes to judgment. In the unloveliness of decay the Middle Ages are as other ages have been, as our own will be: but in those ages there was more than one outburst of life; more than once the enthusiasm of the youth of the West went out to explore the ways of the realm of ideas; and, if we believe ourselves at last to have found the only thoroughfare, we owe this knowledge to those who before us travelled the uncharted seas. If we have inherited a great commerce and dominion of science it is because their argosies had been on the ocean, and their camels on the desert. “Discipulus est prioris posterior dies”; man cannot know all at once; knowledge must be built up by laborious generations. In all times, as in our own, the advance of knowledge is very largely by elimination and negation; we ascertain what is not true, and we weed it out. To perceive and to respect the limits of the knowable we must have sought to transgress them. We can build our bridge over the chasm of ignorance with stored material in which the thirteenth century was poor indeed, we can fix our bearings where then was no foundation; yet man may be well engaged when he knows not the ends of his work; and the schoolmen in digging for treasure cultivated the field of knowledge, even for Galileo and Harvey, for Newton and Darwin. Their many errors came not of indolence, for they were passionate; not of hatred of light, for they were eager for the light; not of fickleness, for they wrought with unparalleled devotion; nor indeed of ignorance of particular things, for they knew many things: they erred because they did not know, and they could not know, the conditions of the problems which, as they emerged from the cauldron of war and from the wreck of letters and science, they