32 THE FACTORS OF TUli MIND

The headmaster gives my argument a different t urn. He
writes : " those boys who did best were the younger and
more conscientious workers " ; and for him, it appears, the
" essential cause of success " is rather a quality of character
than of intelligence—a general factor of conscientiousness.
The pupils' own class teacher offers yet another explana-
tion : the student has declared that there is a factor common
to the educational tests and the psychological tests, and
infers that it is the ability measured by the latter that
constitutes the common cause ; the teacher, accepting the
same premiss, puts cause and effect the other way round :
it is, he urges, not the psychological ability that Ixas produced
the educational skill; it is the skill measured by the educa-
tional tests, i.e. the skill imparted by his own teaching, that
has enabled the pupils to solve the psychological problems,

If, however, instead of dividing the tests into educational
and psychological, we classify them according to the concrete
nature of the various problems, we can discern quite differ-
ent common factors. Some of the tests, both the psycho-
logical and the educational, involve material that is primarily
visual; others depends largely on memory j others again
require the child to formulate an answer in words of his
own. This suggests a threefold group-factor pattern con-
forming with the requirements of * simple structure ' ; and,
on actual trial, this pattern yields a far closer fit to the
observed correlations than the hypothetical figures deduced
from the writer's own saturation coefficients* On this
basis, therefore, taking each group of tests in turn, we could
argue with equal justice that, not the general factor common
to all the tests, but the particular factor common to each
limited group was the " essential cause of success n within
that limited group.

The main conclusion of the thesis, therefore, is by no
means " confirmed beyond dispute." There are half a
dozen other explanations which would account for the
results just as plausibly. Where precisely, then, has the
fallacy crept in ? At bottom it arises from two time-
honoured errors as to the nature of inductive reasoning,
errors which crop up again and again in factorial arguments :
first, induction is treated as a procedure for reaching certain