PROBLEM OF NURTURE AND NATURE 33 



matter further. I must turn to the main topic of my lecture to-night, 

 and bring up as Francis Galton would himself have wished such 

 vagaries of opinion as I have quoted against the wall of solid statistical 

 fact. 



We have three fundamental questions to answer: 



(i) What do we as Galtonians and Biometricians understand by 

 heredity, and how do we measure it? 



(ii)' What do we of the same school understand by environment? 



(iii) What do members of this Laboratory mean when they assert 

 that nature or heredity is far more important than nurture or 

 environment ? 



First what do we mean by heredity? 



There are to my mind two distinct factors involved under the idea 

 of heredity, which may not unfitly be described as interspecial (or 

 even interracial) heredity and intraspecial (or intraracial) heredity. 

 If every possible human being in a given race were equally likely to 

 be the product of every possible male and female within the race, we 

 as biometricians should assert that there was no heredity in the race. 

 Our measure of heredity is the measure of the extent to which a 

 deviation from average or type within the race is inherited by the 

 progeny. If it is not inherited then there would be no intraracial 

 heredity. We are perfectly aware that this is not the sense given to 

 the word heredity by some biologists, they would attribute to heredity 

 the fact that a goat produces a goat and not a sheep even if the 

 characters of individual goats had no relation to parental deviations 

 from type. The difference in meaning is not a subject for dispute, 

 but a question of definition, of a proper understanding of the use of 

 terms in a particular context. For a Galtonian heredity or better 

 intraspecial heredity is a measure within a definite group of the 

 inheritance of such deviations from type as actually occur within 

 the group. 



Secondly what does the Biometric School understand by "environ- 

 ment"? Certainly their idea of it is not identical with the silly sort 

 of notion by which certain biologists consider they can demonstrate 

 that nurture is more important than nature. Without environment 

 they state an organism could not survive at all, hence environment 

 must be more important than heredity. We might cap such an 

 argument by asserting that as supermen would produce supermen, and 

 as no environment has yet produced a superman heredity must be 

 more effective than environment ! What the biometrician understands 



