THE REAL ERROR OF CYRIL BURT 345
unintentionally amusing aside, Thurstone once mused over the
technical differences between Burt and himself, and decided that
Burt's propensity for algebraic rather than geometrical represen-
tation of factors arose from his deficiency in the spatial PMA:
The configurational interpretations are evidently distasteful to Burt,
for he does not have a single diagram in his text. Perhaps this is indicative
of individual differences in imagery types which lead to differences in
methods and interpretation among scientists (1947, p. ix).- Burt and Spearman based their psychological interpretation
of factors on a belief that g was dominant and real—an innate, gen-
eral intelligence, marking a person's essential nature. Thurstone's
analysis permitted them, at best, a weak second-order g. But sup-
pose they had prevailed and established the inevitability of a dom-
inant g? Their argument still would have failed for a reason so
basic that it passed everybody by. The problem resided in a logical
error committed by all the great factorists I have discussed—the
desire to reify factors as entities. In a curious way, the entire history
that I have traced didn't matter. If Burt and Thurstone had never
lived, if an entire profession had been permanently satisfied with
Spearman's two-factor theory and had been singing the praises of
its dominant g for three-quarters of a century since he proposed it,
the flaw would be as glaring still.
The fact of pervasive positive correlation between mental tests
must be among the most unsurprising major discoveries in the his-
tory of science. For positive correlation is the prediction of almost
every contradictory theory about its potential cause, including both
extreme views: pure hereditarianism (which Spearman and Burt
came close to promulgating) and pure environmentalism (which no
major thinker has ever been foolish enough to propose). In the
first, people do jointly well or poorly on all sorts of tests because
they are born either smart or stupid. In the second, they do jointly
well or poorly because they either ate, read, learned, and lived in
an enriched or a deprived fashion as children. Since both theories
predict pervasive positive correlation, the fact of correlation itself
can confirm neither. Since g is merely one elaborate way of
expressing the correlations, its putative existence also says nothing
about causes.