But on these grounds his argument is shaky. As Clark Glymour puts it, "Gould claims that factor analysis produces conjectures about the existence of unobserved properties solely because the properties, if they existed, would explain features of data; in his phrasing factor analysis 'reifies' unobserved quantities, and he thinks 'reification' is a Big Mistake. I wonder whether he thinks atoms and molecules and their weights are Big Mistakes as well, and if not, why not." (Scientists Respond the Bell Curve, p. 259)
What makes Gould's argument fascinating is his explication of the metaphor of the mind which drove Spearman to discover a method--factor analysis-- by which to derive from a battery of tests g.
"Thus caught up in physics envy again, Spearman described his own 'adventurous step of deserting all actually observable phenomena of the mind and proceeeding instead to invent an underlying something which --by analogy with physics--has been called mental energy.'. Spearman looked to the basic property of g--its influence in varying degree, upon mental operations--and tried to imagine what physical entity best fitted such behavior. What else, he argued, but a form of energy pervading the entire brain and activitating a set of specific 'engines,' each with a definite locus. The more energy, the more general activation, the more intelligence...If g pervades the entire cortex, as a general energy, then the s-factors for each test must have more definite locations. They must represent specific groups of neurons, activating in different ways by the energy identified with g. The s-factors, Spearman wrote (and not merely in metaphor), are engines fueled by a circulating g." (Mismeasure of Man, 296).
Best, Rakesh