We shall begin, then, with the lower forms, dwelling upon these at some length, because they are usually neglected, or altogether omitted. This is the _pre-linguistic_ period of abstraction and generalisation: words are totally wanting; they are an unknown factor. How far is it possible without the aid of language to transcend the level of perception, and of consecutive images, and to attain a more elevated intellectual standpoint? In replying empirically, we have three fairly copious sources of information: animals, children who have not yet acquired speech, and uneducated deaf-mutes. ANIMALS. It is a commonplace to say that animal psychology is full of obscurities and difficulties. These arise mainly with regard to the question now occupying us; for we are concerned with ascertaining, not whether animals perceive, remember, and even, when their organisation is sufficiently advanced, imagine (which no one denies), but if they are capable in the intellectual order of still better and greater achievements. The common opinion is in the negative; yet this may rest entirely upon ambiguity of language. Without prejudging anything, we must interrogate the facts to hand, and link them as closely as possible in our interpretation. As to the facts themselves we may be sparing of detail; they are to be found in special treatises, and it is superfluous to repeat them in these pages. It is moreover evident that a large portion of the animal kingdom may be neglected. In its lowest regions it is so remote from us, and has so obscure and scant a psychology, that nothing can be learned from it. In the higher forms alone can we have any chance of finding what we seek, i. e., (1) equivalents of concepts, (2) processes comparable with reasoning. In the immense realm of the invertebrates, the highest psychical development is, by general acknowledgment, met with among the social Hymenoptera; and the capital representatives of this group are the ants. To these we may confine ourselves. Despite their tiny size, their brain, particularly among the neuters, is remarkable in structure—“one of the most marvellous atoms,” says Darwin, “in all matter, not excepting even the human brain.” Injuries to this organ, which are frequent in their sanguinary combats, cause disorders quite analogous to those observed in mammals. It is useless to recall what every one knows of their habits: their organisation of labor, varied methods of architecture, their wars, plundering and rape, practice of slavery, methods of education, and (in certain species) their agricultural labors, harvesting, construction of granaries,[10] etc. We, on the contrary, must examine the exceptional cases in which the ants depart from their general habits; for their ability to abstract, to generalise, and to reason, can only be established by new adaptations to unaccustomed circumstances. The following may serve as examples: