186 SECTIONAL ADDRESSES 
problems of the individual are the problems of society and vice versa : 
a man is not independent of his fellows ; his social environment is part of 
himself ; his thoughts, feelings and desires vary with his environment ; 
he is socially a chameleon, and any account of him which fails to consider 
his environment is as distorted as is an account of society itself which fails 
to consider the variety of aptitudes, motives, knowledge, manners and 
customs of its members. A social group is a complex structure which 
contains within itself other groups and sub-groups, professional, economic, 
linguistic, etc., whose harmonious co-operation is necessary for the welfare 
of the whole. The big social problem is the dual one of fitting the 
individual into the group and fitting the group to the individual. This is 
essentially an educational problem, one for education in the widest sense 
of the word ; it concerns the home, the school, the university, the press, 
and the broadcasting and other publicity agencies. Its solution demands 
some knowledge of the natural endowment of the individual, his impulses 
and intellectual capacities, and of methods of making the most of them ; 
and this in its turn implies the need for and the use of methods of assessing 
human endowment and achievement. 
I wish to consider especially the scientific assessment of natural capacity 
and some of the problems connected with it, therefore, it is necessary to 
keep clearly in mind the distinction between ability and capacity. Ability is 
actual, capacity is potential. Ability is measured by what can be done here 
and now ; capacity can usually be estimated by what can be done after a 
course of training. Knowledge and skill at games are forms of ability ; 
they depend on certain natural capacities and on upbringing. All 
examinations are tests of ability. 
The satisfactory measurement of ability is always difficult on account 
of the adaptability of the human organism. ‘The measurement of the 
efficiency of an engine is by comparison a very trivial affair. Even the 
best of examinations gives a somewhat blurred estimate of human mental 
ability. 
The measurement of ability is difficult enough, but the estimation of the 
parts played by native capacity and upbringing respectively in determining 
such ability is very much more so. Innate qualities do not exist im vacuo : 
they exist with reference to certain external conditions and they must be 
diagnosed and measured in relation to these conditions. Every test is 
directly a test of ability, and can be a test of capacity only indirectly. 
Where training has no effect on the expression of a capacity, then a test 
of ability is a test of capacity ; but few, if any, capacities are unaffected 
by training. If opportunities and incentives are so widely scattered that 
they are available for everybody, or if similar training has been given to 
all, then differences in performance indicate differences in capacity ; but 
where the essential training and environmental conditions vary, inferences 
regarding capacity can be made with much less certainty. It is difficult 
to convince oneself regarding the uniformity of external conditions and easy 
to blunder : for example, it is sometimes supposed that mental differences 
between children of the same parents are due solely to genetic differences, 
but some of them are certainly due to variations in the family environment : 
the health and age of the mother are not the same at the birth of each child 
