448 THE HISTORY OF BIOLOGY 



Good progress had already been made when science was backed by such 

 sound victories as Mayer's law of energy and Wohler's organic syntheses. 



German materialism 

 It was in these circumstances that the new realistic natural philosophy arose, 

 whose different ideas have occupied the attention of so many thinkers and 

 writers up to the present day, and which has gone under so many different 

 names, such as positivism, materialism, monism, agnosticism, and other 

 isms. Its main characteristic has been the endeavour to build up, on an exact 

 natural-scientific basis, an explanation of the whole 0/ existence — that is, to 

 base on the limited results of research an explanation of the illimitable, by 

 means of weights and measures to explain the immeasurable and imponder- 

 able. These natural explanations might have been fully justified as expressions 

 of a personal view of life, if their originators had clearly realized the differ- 

 ence between facts and hypotheses, between manifestations that are actually 

 capable of being observed and turned to practical use, and theoretical con- 

 structions of such as are inaccessible to any observation whatsoever. This clear 

 thinking, however, has unfortunately been somewhat rare; far more common 

 has been the tendency to work up explanations of nature and then insist upon 

 having them regarded as the results of natural-scientific research — a weak- 

 ness that has often been apparent in men who in their own special sphere 

 have been keen and conscientious observers. From the outset this temptation 

 was no doubt due to the influence of romantic philosophy, which had con- 

 fidently proclaimed the infallibility of its absolute natural explanations. 

 Another factor, especially as regards the more popular scientific literature, 

 was the rivalry with the ecclesiastical tenets, which maintained the absolute 

 truth of the words of Scripture, even in questions of natural science. And, 

 finally, there were in Germany the political points of view to be reckoned 

 with; the ruling powers did their utmost to preserve the old belief in au- 

 thority, which was considered to conduce to obedience to government; the 

 opponents of this belief were consequently on the side of natural science. 

 The contrast was still further sharpened by the revolutionary outbreak of 

 1848 and was by no means softened by the stern measures which the Govern- 

 ments adopted after their victory, in order to maintain their authority. Con- 

 siderable light is thrown upon these conditions by the so-called materialist 

 dispute in the beginning of the eighteen-fifties, a controversy which not 

 only caused great excitement at the time, but also produced after efi^ects that 

 have been felt ever since. It may therefore be worth glancing at, all the more 

 so as the parties to the dispute were exclusively scientific investigators, some 

 of whom were very distinguished, while philosophical and theological 

 opinions do not come into consideration at all. 



Among those who became involved in this dispute Justus Liebig (1803- 

 73) ranks first; on thewhole, he may be considered one of the greatest scientists 



