The Nature of "Intelligence" and the Principles of Cognition

Spearman's central claim is that psychology can become a rigorous science by identifying universal laws of cognition, just as physics identifies laws of motion. He proposes three qualitative laws of noegenesis: the apprehension of experience, the eduction of relations, and the eduction of correlates . These laws describe how new knowledge is generated rather than merely reproduced. Spearman rejects associationism, which he saw as reducing thought to passive connections among ideas. He also rejects the view that psychology must remain a descriptive or introspective discipline without lawful structure. In his own words, the book aimed to supply 'the so long missing genuinely scientific foundation for psychology' .

The book introduced noegenesis — the three laws of knowledge origination that Spearman believed govern all cognitive activity. The first law, apprehension of experience, concerns the encoding of sensory or internal data. The second, eduction of relations, describes inferring the connection between apprehended items. The third, eduction of correlates, concerns applying a known relation to generate a new item . Spearman argued that individual differences in the speed and accuracy of these operations constitute the 'g' factor. Noegenesis remains historically significant for grounding psychometric findings in cognitive theory, though the specific laws have not survived as active research programs.

R. G. Collingwood reviewed the book in 1923 and launched an attack that he expanded in his Essay on Metaphysics (1940). His central charge was that psychology generally, and psychometrics by implication, was a 'fashionable scientific fraud' . Joel Michell's analysis notes that Collingwood identified defects in psychometric thinking that subsequently became entrenched, though Michell argues Collingwood's own logical and metaphysical views are unsustainable . Ironically, some elements of Collingwood's philosophy — his 'fallacy of calculation' and concept of 'scale of forms' — are relevant to psychometrics. The critique is notable as one of the earliest sustained philosophical attacks on the discipline Spearman helped found.

The Nature of 'Intelligence' (1923) precedes The Abilities of Man (1927) and provides its cognitive foundation. The 1923 book establishes the qualitative laws of noegenesis, while the 1927 work focuses on the quantitative two-factor theory and the tetrad equation . Spearman conceived 'g' as neural energy fueling the three noegenetic processes, so the later statistical work depends on the earlier theoretical architecture. The 1923 book also frames psychology as a science with laws comparable to physics, a theme the later book develops through more extensive empirical evidence. Together they form Spearman's mature system.

Spearman believed psychology suffered from a lack of general laws, unlike physics, which had advanced by discovering universal principles. The book's opening promise — that psychology could finally take its place 'along with the other solidly founded sciences, even physics itself' — reflects this ambition. The three noegenetic laws were meant to function like physical laws: universal, precise, and generative of testable predictions. A 1924 review in Revue Philosophique de Louvain noted that the book presents psychology as taking on 'an appearance of the same genre as the physical sciences' . This aspiration drew criticism from those who doubted psychology's subject matter could sustain such laws.

Noegenesis is not an active research framework in contemporary cognitive psychology. The term and the three laws appear in historical accounts of Spearman's work and in psychometric textbooks discussing the theoretical basis of 'g' . The laws' core insight — that intelligence involves relational reasoning beyond mere association — has been absorbed into broader cognitive theories, particularly those emphasizing analogical reasoning and fluid intelligence. However, Spearman's specific formulation, with its claim that these operations constitute a single general factor, has been challenged by multiple-factor theories. The book remains valuable as a historical document showing how early psychometricians attempted to connect statistical findings to cognitive theory.