Xll INTRODUCTION 



than metaphysically, on the basis of a study of the successive 

 changes in matter which preceded the appearance of life and 

 led to its emergence. Matter never remains at rest, it is con- 

 stantly moving and developing and in this development it 

 changes over from one form of motion to another and yet 

 another, each more complicated and harmonious than the 

 last. Life thus appears as a particular very complicated form 

 of the motion of matter, arising as a new property at a definite 

 stage in the general development of matter. 



As early as the end of last century Frederick Engels indi- 

 cated that a study of the history of the development of matter 

 is by far the most hopeful line of approach to a solution of 

 the problem of the origin of life. These ideas of Engels were 

 not, however, reflected to a sufficient extent in the scientiftc 

 thought of his time. 



Even in the first decades of this century only a very few 

 of the leading scientists came out in support of the idea that 

 life originated as the result of an evolutionary process. Their 

 pronouncements were, however, still of a very general charac- 

 ter and could not overcome the stagnation in the scientific 

 fields concerned with the problem of the origin of life. 



Scientists have acquired a large number of facts during 

 the twentieth century and it is only on the basis of these that 

 we have now, at last, been able to draw a schematic picture 

 of the evolutionary development of matter and set out the 

 stages through ^vhich it must successively have progressed 

 on the way to the emergence of life. As a result of this, wide 

 possibilities for experimental work on the problem of the 

 origin of life have been opened up. This time, though, 

 interest was not focussed on hopeless attempts to discover 

 instances of spontaneous generation but on the study and 

 experimental reproduction of phenomena which were not 

 merely possibilities but were completely subject to natural 

 laws and took place successively in the evolutionary develop- 

 ment of matter. 



This situation gave rise to a complete recasting of the 

 ideas of scientists in relation to the problem of the origin 

 of life. During the course of nearly all the first half of the 

 twentieth century this problem was almost entirely excluded 

 from the domain of science and it only received an insignifi- 



