For all knowledge is founded on observation, and proceeds from this by analysis, by synthesis and analysis, by induction and deduction, and if possible by verification, or by new appeals to observation under the guidance of deduction—by steps which are indeed correlative parts of one method; and the ancient sciences afford examples of every one of these methods, or parts of one method, which have been generalized from the examples of science.A failure to employ or to employ adequately any one of these partial methods, an imperfection in the arts and resources of observation and experiment, carelessness in observation, neglect of relevant facts, by appeal to experiment and observation—these are the faults which cause all failures to ascertain truth, whether among the ancients or the moderns; but this statement does not explain why the modern is possessed of a greater virtue, and by what means he attained his superiority.