The true object, therefore, of the investigation of nature is not, as the Greek philosophers held, speculative satisfaction, but to establish the reign of man over nature; and this Bacon judged to be attainable, provided new methods of attacking the problems were introduced. Whatever may be thought of his daring act in bringing natural science down from the clouds and assigning to her the function of ministering to the material convenience and comfort of man, we may criticise Bacon for his doctrine that every branch of science should be pursued with a single eye towards practical use. Mathematics, he thought, should conduct herself as a humble, if necessary, handmaid, without any aspirations of her own. But it is not thus that the great progress in man's command over nature since Bacon's age has been effected. Many of the most valuable and surprising things which science has succeeded in doing for civilisation would never have been performed if each branch of knowledge were not guided by its own independent ideal of speculative completeness. [Footnote: This was to be well explained by Fontenelle, Preface sur l'utilite des mathematiques, in Oeuvres (ed. 1729), iii, I sqq.] But this does not invalidate Bacon's pragmatic principle, or diminish the importance of the fact that in laying down the utilitarian view of knowledge he contributed to the creation of a new mental atmosphere in which the theory of Progress was afterwards to develop. 3. Bacon's respect for the ancients and his familiarity with their writings are apparent on almost every page he wrote. Yet it was one of his principal endeavours to shake off the yoke of their authority, which he recognised to be a fatal obstacle to the advancement of science. "Truth is not to be sought in the good fortune of any particular conjuncture of time"; its attainment depends on experience, and how limited was theirs. In their age "the knowledge both of time and of the world was confined and meagre; they had not a thousand years of history worthy of that name, but mere fables and ancient traditions; they were not acquainted with but a small portion of the regions and countries of the world." [Footnote: Nov. Org. i. 84; 56, 72, 73, 74.] In all their systems and scientific speculation "there is hardly one single experiment that has a tendency to assist mankind." Their theories were founded on opinion, and therefore science has remained stationary for the last two thousand years; whereas mechanical arts, which are founded on nature and experience, grow and increase.