The certainty indeed of conclusions on such subjects was out of harmony with the grandest feature of Bacon's work, his noble confession of the liability of every enquirer to error. It was his especial task to warn men against the "vain shows" of knowledge which had so long hindered any real advance in it, the "idols" of the Tribe, the Den, the Forum, and the Theatre, the errors which spring from the systematizing spirit which pervades all masses of men, or from individual idiosyncrasies, or from the strange power of words and phrases over the mind, or from the traditions of the past. Nor were the claims of theology easily to be reconciled with the position which he was resolute to assign to natural science. "Through all those ages," Bacon says, "wherein men of genius or learning principally or even moderately flourished, the smallest part of human industry has been spent on natural philosophy, though this ought to be esteemed as the great mother of the sciences; for all the rest, if torn from this root, may perhaps be polished and formed for use, but can receive little increase." It was by the adoption of the method of inductive enquiry which physical science was to make its own, and by basing enquiry on grounds which physical science could supply, that the moral sciences, ethics and politics, could alone make any real advance. "Let none expect any great promotion of the sciences, especially in their effective part, unless natural philosophy be drawn out to particular sciences; and, again, unless these particular sciences be brought back again to natural philosophy. From this defect it is that astronomy, optics, music, many mechanical arts, and (what seems stranger) even moral and civil philosophy and logic rise but little above the foundations, and only skim over the varieties and surfaces of things." It was this lofty conception of the position and destiny of natural science which Bacon was the first to impress upon mankind at large. The age was one in which knowledge was passing to fields of enquiry which had till then been unknown, in which Kepler and Galileo were creating modern astronomy, in which Descartes was revealing the laws of motion, and Harvey the circulation of the blood. But to the mass of men this great change was all but imperceptible; and it was the energy, the profound conviction, the eloquence of Bacon which first called the attention of mankind as a whole to the power and importance of physical research. It was he who by his lofty faith in the results and victories of the new philosophy nerved its followers to a zeal and confidence equal to his own. It was he above all who gave dignity to the slow and patient processes of investigation, of experiment, of comparison, to the sacrifice of hypothesis to fact, to the single aim after truth, which was to be the law of modern science. [Sidenote: Advance of the Parliament.]