The first of these arguments and the one which in general makes the greatest impression, contrasts the instinct of animals with the intelligence of man. It represents instinct as blind and fatal, and intelligence as free and progressive. But this antithesis cannot withstand the examination of facts. Instinct is called too hastily a “fatal tendency of animals to the mechanical execution of actions which are uniformly determined by corresponding circumstances, and not requiring nor even admitting of any education properly so-called.” This fatal tendency does not exist. It is a gratuitous supposition, perhaps a remnant of the Cartesian theory concerning the automatism of animals. Georges Leroy, in his charming _Lettres sur les animaux_, has shown that in the mammals and in the birds of our districts, the fixity in the construction of habitations, in the habits of hunting, in the mode of migration, etc., only existed for naturalists who never left their study, or for inattentive observers.[209] Undoubtedly, habits may become hereditary. But here we only have a phenomenon common to men and animals, and those habits are modified if the circumstances which have produced them come to change. It is in this sense alone that we can admit M. de Blainville’s formula: “L’instinct est la raison fixée, la raison est l’instinct mobile.” We must especially understand that instinct is not opposed to intelligence. What ought we really to indicate by instinct? A spontaneous impulse in a direction determined, independently of any foreign influence.” But in this sense, the word applies to the activity of any faculty whatever, to the intellectual faculties as well as to the others. There is no contrast between instinct and intelligence. We say of a child that he has the “instinct” of music, of drawing, of calculation, etc. In this sense man has certainly as many and more instincts than animals. If, on the other hand, we call intelligence the faculty of modifying our conduct according to the circumstances of each case, animals are, like man, more or less intelligent and reasonable. Otherwise they would be doomed to disappear very quickly. But animals have no language! Another error in observation. The higher animals have a certain degree of language corresponding to the nature and to the extent of their relations. This language is no more fixed than the so-called instincts. The language of each social species is characterised by an arrest of development precisely like the society which this species tended to found. The limits of its progress, beyond which indeed it does not go, result from the whole of the obstacles which it encounters, in consequence of the competition with the other species, and particularly with the human species, without naming those limits which the imperfection of organs may create.[210]