296 THE SIGNIFICANCE OF SEXUAL REPRODUCTION 



matter and force. In no single group of phenomena can we begin 

 with the investigation of ultimate causes, because at this very point 

 our means of reasoning stop short. We cannot begin with ulti- 

 mate phenomena and gradually lead up to those which are more 

 complicated : we cannot proceed synthetically and deductively, 

 building up the phenomena from below ; but we must as a rule 

 proceed analytically and inductively, proceeding from above down- 

 wards. 



No one will dispute these statements, but they are often for- 

 gotten, as is proved by the above-mentioned objection. If we 

 were only permitted to attack the more complicated phenomena 

 after gaining a complete insight into the simpler ones, then all 

 scientists would be physicists and chemists, and not until Physics 

 and Chemistry were done with should we be permitted to proceed 

 to the investigation of organic nature. Under these circumstances 

 we ought not to possess now any scientific theory of medicine ; 

 for the study of pathological physiology could not be commenced 

 until normal physiology was completely known and understood. 

 Yet how great a debt is owing by normal to pathological physio- 

 logy ! This is an example which enforces the conclusion that it 

 is not only permissible, but in the highest degree advantageous, for 

 the different spheres of phenomena to be attacked simultaneously. 



Furthermore, if we had been compelled to proceed from the 

 simple to the complex, what would have become of the Theory of 

 Descent, the influence of which has advanced our knowledge of 

 Biology to an altogether immeasurable extent ? 



But in this often repeated criticism that we are not yet ready to 

 attack such complicated phenomena as heredity, is hidden still 

 another fallacy, for it is implied that facts become less certain in 

 proportion to the complexity of their causes. But is it less certain 

 that the egg of an eagle developes into an eagle, or that the pecu- 

 liarities of the father and mother are transmitted to the child, than 

 that a stone falls to the ground when its support is taken away ? 

 Again, is it not possible to draw a perfectly distinct and certain 

 conclusion as to the relative quantity of the material basis of 

 heredity, present in the germ-cells of either parent, from the fact 

 that the father and mother possess an equal or nearly equal share 

 in heredity ? But it is really unnecessary to argue in this way : 

 why should we do more than re-affirm that such a method of pro- 



