We have seen that Newton, along with views the most just and important concerning the nature and methods of science, had something of the tendency, prevalent in his time, to suspect or reject, at least speculatively, all elements of knowledge except observation. This tendency was, however, in him so corrected and restrained by his own wonderful sagacity and mathematical habits, that it scarcely led to any opinion which we might not safely adopt. But we must now consider the cases in which this tendency operated in a more unbalanced manner, and led to the assertion of doctrines which, if consistently followed, would destroy the very foundations of all general and certain knowledge. FOOTNOTES: [Footnote 217: _Optics_, qu. 31, near the end.] [Footnote 218: Qu. 28.] [Footnote 219: _Hist. Ind. Sc._ b. v. and b. vii.] [Footnote 220: _Optics_, qu. 31.] [Footnote 221: _History of Ideas_, b. iii. c. x.] [Footnote 222: _Ibid._ b. iii. c. ix. x. xi.] [Footnote 223: _Opticks_, qu. 31.] [Footnote 224: _Nov. Org._ l. ii. Aph. 2. "Licet enim in natura nihil existet præter corpora individua, edentia actus puros individuos ex lege; in doctrinis tamen illa ipsa lex, ejusque inquisitio, et inventio, et explicatio, pro fundamento est tam ad sciendum quam ad operandum. Eam autem _legem_, ejusque _paragraphos, formarum_ nomine intelligimus; præsertim cum hoc vocabulum invaluerit, et familiariter occurrat." Aph. 17. "Eadem res est _forma_ calidi vel _forma_ luminis, et _lex_ calidi aut _lex_ luminis."] CHAPTER XIX. LOCKE AND HIS FRENCH FOLLOWERS. 1. In the constant opposition and struggle of the schools of philosophy, which consider our Senses and our Ideas respectively, as the principal sources of our knowledge, we have seen that at the period of which we now treat, the tendency was to exalt the external and disparage the internal element. The disposition to ascribe our knowledge to observation alone, had already, in Bacon's time, led him to dwell to a disproportionate degree upon that half of his subject; and had tinged Newton's expressions, though it had not biassed his practice. But this partiality soon assumed a more prominent shape, becoming extreme in Locke, and extravagant in those who professed to follow him.