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SCIENTIFIC THOUGHT. 



v not as clear as it has become since, and the work has 

 also been superseded by more detailed labours, espe- 

 cially of German historians. 1 The ' Philosophy of the In- 

 ductive Sciences,' by the same author, was written with 

 the object of doing something towards determining the 

 nature and conditions of human knowledge, and had 

 thus a philosophical rather than a historical object in 

 view. The same can be said of Mill's ' Logic,' of Comte's 

 ' Philosophic positive,' and of more recent works such 

 as Jevons's ' Principles of Science.' They form an im- 

 portant section of the philosophical literature of our 

 century, and on future occasions I shall frequently have 

 to refer to their teaching. At present I am not about 

 to investigate the eternal principles of correct reason- 

 ing, and the particular methods adopted, consciously or 

 unconsciously, by scientific writers of all times. What 

 I desire to do is, to enumerate and analyse briefly the 

 changing ideas, the general views, under the guidance 

 of which scientific work has progressed in the course 

 of this century. No doubt the same object was before 



1 Besides the works on the his- 

 tory of the special sciences con- 

 tained in the Munich Collection, 

 ' Geschichte der Wissenschaften in 

 Deutschland,' which in many in- 

 stances is not limited to German 

 science and learning, there is the 

 unique ' Geschichte der Chemie,' 

 by Hermann Kopp (Braunschweig, 

 4 vols., 1843-47), the ' Geschichte 

 der Physik,' by Rosenberger (Braun- 

 schweig, 3 vols., 1882-90), and 

 Haser's ' Geschichte der Medicin ' 

 (Wien, 1875-82, 3rd ed.) In addi- 

 tion to the numerous works of Ger- 

 man specialists, I must mention as of 

 the first importance and value the 

 histories by the late Isaac Todhunter 



of the ' Theory of Attraction and 

 Figure of the Earth' (2 vols., 

 1873), the ' Calculus of Variations ' 

 (1861), the 'Theory of Probability' 

 (1865), and the 'Theory of Elastic- 

 ity' (continued by K. Pearson, 2 

 vols. in 3 parts, 1886-93). They 

 supply the want of a good history 

 of modern mathematics, which does 

 not exist. Lastly, the "Deutsche 

 Mathematiker-Vereinigung " have 

 published in their Jahrbuch valu- 

 able histories of special branches of 

 mathematics notably the ' Theory 

 of Invariants ' by Franz Mayer, and 

 the ' Modern Theory of Functions ' 

 by Brill and Noether. 



