64 FRAGMENTS OF SCIENCE. 



And here, in passing, I would notice a point which is 

 well Avorthy of attention. Kepler had deduced his laws 

 from observation. As far back as those observations ex- 

 tended, the planetary motions had obeyed these laws ; and, 

 neither Kepler nor Newton entertained a doubt as to their 

 continuing to obey them. Year after year, as the ages 

 rolled, they believed that those laws would continue to 

 illustrate themselves in the heavens. But this was not suf- 

 ficient. The scientific mind can find no repose in the mere 

 registration of sequence in Nature. The further question 

 intrudes itself with resistless might : whence comes the se- 

 quence ? What is it that binds the consequent with its an- 

 tecedent in Nature ? The truly scientific intellect never can 

 attain rest until it reaches the forces by which the observed 

 succession is produced. It was thus with Torricelli ; it was 

 thus with Newton ; it is thus preeminently with the real 

 scientific man of to-day. In common with the most igno- 

 rant, he shares the belief that spring will succeed winter, 

 that summer will succeed spring, that autumn will succeed 

 summer, and that winter will succeed autumn. But he 

 knows still further — and this knowledge is essential to his 

 intellectual repose — that this succession, besides being per- 

 manent, is, under the circumstances, necessary y that the 

 gravitating force exerted between the sun, and a revolving 

 sphere with an axis inclined to the plane of its orbit, must 

 produce the observed succession of the seasons. Not until 

 this relation between forces and phenomena has been es- 

 tablished is the law of reason rendered concentric with the 

 law of Nature, and not until this is effected does the mind 

 of the scientific philosopher rest in peace. 



The expectation of likeness, then, in the procession of 

 phenomena is not that on which the scientific mind founds 

 its belief in the order of Nature. If the force be permanent 

 the phenomena are necessary, whether they resemble or do 

 not resemble any thing that has gone before. Hence, in 



