Mark Holloway, in his biography of Norman Douglas, makes the following observation:
It is a mark of Douglas’ lively intelligence (as distinct from his intellectual ability) that he seldom failed to learn the lessons that he felt were suited to his temperament …
As a young man, Douglas was a keen amateur naturalist. Just before leaving school he met the eminent zoologist Franz Leydig, who made just such a formative impression on him:
What I liked about his books and pamphlets was not so much his minute histological researches, clear-cut description, and the admirable drawings done by himself; it was something else; his a s i d e s, his footnotes to the text, his generalisations. He would indulge in an excursus of “historical and critical remarks” on some species and even go into details about those artists who have successfully reproduced its shape; he would open up unexpected vistas, citing copiously from authorities old and new. This extensive documentation testified not only to wide reading, but to a wide outlook. His suggestiveness is what attracted me to Leydig. He was no ordinary Professor; he was something more comprehensive, more human.quoted in Holloway, p. 64
Holloway adds that
It was Leydig’s strong emphasis on individuality that impressed Norman most. He was interested in differences of character between animals of the same species, and observed them among his dogs and among his pet birds and reptiles. He thought individuality should be fostered and not repressed …
and counselled Douglas against university for that reason, though himself a professor.
As Holloway says, this “suggestiveness” is a hallmark of Douglas’s style, the broad outlook, the “quality of continual reference to the greater world beyond the immediate subject”. That is the individual cast of his mind, even when he turned to diverse subject-matter.
All this brought to mind my aperçu that stupidity is a moral failing. The aphorism loses its pointe by tedious explanation, but the distinction above is obviously pertinent. I would add that the salient characteristic of a lively intelligence, as it unfolds and flourishes over time and circumstance, is a sympathy for its own individuality. There is an affinity between those whose casts of mind are distinctive, which does not lie in mutual similarity, but distance from the herd. It can be recognised, and should be fostered, in children, who are apt to have it knocked or smothered out of them.