Mere numbers cannot bring out... the intimate essence of the experiment. This conviction comes naturally when one watches a subject at work ... What … - Alfred Binet

When we attempt to understand the inmost nature of the outer world, we stand before it as before absolute darkness. There probably exists in nature, outside of ourselves, neither colour, odour, force, resistance, space, nor anything that we know as sensation. Light is produced by the excitement of the optic nerve, and it shines only in our brain; as to the excitement itself, there is nothing to prove that it is luminous; outside of us is profound darkness, or even worse, since darkness is the correlation of light. In the same way, all the sonorous excitements which assail us, the creakings of machines, the sounds of nature, the words and cries of our fellows are produced by excitements of our acoustic nerve; it is in our brain that noise is produced, outside there reigns a dead silence. The same may be said of all our other senses. ...In short, our nervous system, which enables us to communicate with objects, prevents us, on the other hand, from knowing their nature. It is an organ of relation with the outer world; it is also, for us, a cause of isolation. We never go outside ourselves. We are walled in. And all we can say of matter and of the outer world is, that it is revealed to us solely by the sensations it affords us, that it is the unknown cause of our sensations, the inaccessible excitant of our organs of the senses, and that the ideas we are able to form as to the nature and the properties of that excitant, are necessarily derived from our sensations, and are subjective to the same degree as those sensations themselves.

This test thought out and proposed by Professor Ebbinghaus of Berlin, varies in significance according to its mode of use. It consists essentially in this: a word of a text is omitted and the subject is asked to replace it. The nature of the intellectual work by which the gap is filled, varies according to the case. This may be a test of memory, a test of style, or a test of judgment. In the sentence: ‘Louis IX was born in ——‘ the gap is filled by memory. ‘The crow —– his feathers with his beak’; in this the idea of the suppressed word is not at all obscure, and the task consists in finding the proper word. We may say in passing, that according to the opinion of several teachers before whom we have tried it, this kind of exercise furnishes excellent scholastic training. Lastly, in sentences of the nature of those we have chosen, the filling of the gaps requires an attentive examination and an appreciation of the facts set forth by the sentence. It is therefore an exercise of judgment.

Comprehension, inventiveness, direction, and criticism: intelligence is contained in these four words.