148 SCIENCE AND PHILOSOPHY OF THE ORGANISM 



allows us to compare biology with other natural sciences : 

 there is still something more, there is one kind of assump- 

 tion or postulate, or whatever you may choose to call it, 

 without which all science whatever would be altogether 

 impossible. I refer to the concept of universality. All 

 concepts about nature which are gained by positive con- 

 struction out of elements resulting from analysis, claim to 

 be of universal validity] without that claim there could 

 indeed be no science. 



Of course this is no place for a lecture on methodology, 

 and it therefore must suffice to make one remark with 

 special regard to our purpose, which we should like to 

 emphasise. Our concept of the harmonious -equipotential 

 system say rather, our concept of the prospective 

 potency itself presumes the understanding that indeed 

 all blasto meres and all stems of Tubularia, including those 

 upon which we have not carried out our experiments, 

 will behave like those we have experimented with ; and 

 those concepts also presume that a certain germ of Echinus^ 

 A, the blastomeres of which were not separated, would have 

 given two whole larvae, if separation had taken place, while 

 another germ, B, which actually gave us two larvae after 

 separation, would only have given one without it. Without 

 this presumption the concept of " potency " is meaningless, 

 and, indeed, every assumption of a " faculty ' or a 

 " possibility " would be meaningless in the whole area of 

 science. 



But this presumption can never be proved ; it can only 

 be postulated. It therefore is only with this postulate that 

 our first proof of vitalism holds ; but this restriction applies 

 to every law of nature. 



