Alfred Binet, answered from the texts and cited to the page.
The question invites the third person, but I will answer in the first. Intelligence, as I understand it, is not a single thing that can be lifted out of a mind and weighed. When Simon and I built our measuring scale, we were careful to say that it does not permit the measure of intelligence in the strict sense, because intellectual qualities are not superposable — they cannot be laid against one another as linear surfaces are measured.1
What the scale gives is a classification, a hierarchy among diverse intelligences, and for the practical purposes that drove us — finding the children in Paris who needed special instruction — that classification is equivalent to a measure.2 What the scale actually captures is more complex than a pure faculty. The result of any given examination depends on several things at once: the intelligence proper, yes, but also acquisitions gained outside school, acquisitions made at school by a fixed date, and the vocabulary a child has absorbed from family and classroom alike.3
To pretend the number reflects intelligence considered separately from all these concrete circumstances would be to claim more than the experiments warrant. At the level of what intelligence fundamentally does, I hold that its proper work is the adjustment of means to an end. The ends we pursue are chosen by our tendencies, our affective and instinctive life; but the means by which we pursue them are combined by intelligence.4
A locksmith called to open a locked door searches his bunch of keys, but he does not try them indiscriminately — he sees at a glance those that will not fit, and his attempts are directed, selected, according to a mechanism that is the very shape of intelligent adaptation.5 Where that directing, selecting activity is weak or absent, as in the cases I studied among the feeble-minded, the person remains stationary, preferring the immediate pleasure of the moment to the more lasting advantage of the morrow, and so cannot accumulate the capital of experience that normal development requires.6
The scale, then, measures a present state — not a fixed and unalterable quantity stamped in a child at birth. It is a diagnosis in order to prescribe a remedy, never a sentence.
This scale properly speaking does not permit the measure of the intelligence, because intellectual qualities are not superposable, and therefore cannot be measured as linear surfaces are measured, but are on the contrary, a classification, a hierarchy among diverse intelligences.The Development of Intelligence in Children
for the necessities of practice this classification is equivalent to a measure.The Development of Intelligence in Children
The result depends: first, on the intelligence pure and simple; second, on extra-scholastic acquisition capable of being gained precociously; third, on scholastic acquisitions made at a fixed date; fourth, on acquisitions relative to language and vocabulary, which are at once scholastic and extra-scholastic.The Development of Intelligence in Children
the end is chosen by our tendencies; but the means for attaining this end are combined by our intelligence; our study must confine itself to the adjustment of means to an end, which is the proper work of the intelligence, and which constitutes adaptation.The Intelligence of the Feeble-Minded
one is like a locksmith called to open a locked door; he searches in his bunch of keys and tries many but he does not try them all indiscriminately, for he sees at a glance those that will not fit; his attempts are not blind, they are directed, selected.The Intelligence of the Feeble-Minded
The mentality of the child, of the imbecile...consists in preferring the immediate pleasure of the moment, to the more lasting pleasure of the morrow, and consequently in developing an activity which does not calculate, does not reflect, and above all does not economize, and which therefore cannot accumulate capital.The Intelligence of the Feeble-Minded