334 THE MISMEASURE OF MAN
different views about the real nature of intelligence—and the
acceptance of one or the other entailed a set of fundamental con-
sequences for the practice of education.
With Spearman's g, each child can be ranked on a single scale
of innate intelligence; all else is subsidiary. General ability can be
measured early in life and children can be sorted according to their
intellectual promise (as in the 11+ examination).
With Thurstone's PMA's, there is no general ability to measure.
Some children are good at some things, others excel in different
and independent qualities of mind. Moreover, once the hegemony
of g was broken, PMA's could bloom like the flowers in spring.
Thurstone recognized only a few, but other influential schemes
advocated 120 (Guilford, 1956) or perhaps more (Guilford, 1959,
p. 477). (Guilford's 120 factors are not induced empirically, but
predicted from a theoretical model—represented as a cube of
dimensions 6x5X4=120—designating factors for empirical stud-
ies to find).
Unilinear ranking of pupils has no place, even in Thurstone's
world of just a few PMA's. The essence of each child becomes his
individuality, Thurstone wrote (1935, p. 53):
Even if each individual can be described in terms of a limited number
of independent reference abilities, it is still possible for every person to be
different from every other person in the world. Each person might be
described in terms of his standard scores in a limited number of independ-
ent abilities. The number of permutations of these scores would probably
be sufficient to guarantee the retention of individualities.
From the midst of an economic depression that reduced many of
its intellectual elite to poverty, an America with egalitarian ideals
(however rarely practiced) challenged Britain's traditional equation
of social class with innate worth. Spearman's g had been rotated
away, and general mental worth evaporated with it.
One could read the debate between Burt and Thurstone as a
mathematical argument about the location of factor axes. This
would be as myopic as interpreting the struggle between Galileo
and the Church as an argument between two mathematically
equivalent schemes for describing planetary motion. Burt certainly
understood this larger context when he defended the 11+ exami-
nation against Thurstone's assault: