Here is what I have elsewhere said upon this question, so long debated, of the _instinct and understanding of animals_. “There is a most complete difference between _instinct_ and _understanding_. “In _instinct_ all is blind, necessary, and invariable. In _understanding_ every thing is elective, conditional, and modifiable. “The beaver which builds its house, and the bird that constructs its nest, act only by instinct. “The dog and the horse, that learn even the meaning of several of our words, and who pay obedience to us, do so by understanding. “In _instinct_ all is innate. The beaver builds without having learned to build: all that he does is from fatality. The beaver builds under the impulsion of a constant and irresistible force. “In _understanding_, every thing results from experience and _instruction_. The dog obeys only because he has learned to obey: he is perfectly free in this respect; for he obeys only because he will obey. “Finally, in regard to _instinct_ every thing is particular. That admirable industry that the beaver exhibits in the construction of his hut, can be employed in no other occupation than the building of his hut. Now, in _understanding_ every thing is general; for the dog could apply the same flexibility of attention, and of conception, which he uses in obeying, to do any other thing. “In animals there are, therefore, two distinct and primary forces—_instinct_ and _understanding_. As long as our conceptions of these forces were confused, all our views and opinions in regard to the actions of animals remained obscure and contradictory. Among these actions, some exhibited man every where superior to the brute; while others appeared to accord to the brute creation the superiority over man—a contradiction almost as deplorable as absurd! By the distinction that separates blind and necessary actions from elective and conditional ones—or, in a word, instinct from intelligence—all contradiction disappears, and order succeeds to confusion. Whatever in animals is _understanding_, does not in any degree approach the excellence of the human understanding; and whatsoever, under the appearance of _understanding_, seemed superior to the human understanding, is in fact a mere result of a mechanical and blind force.”[187] Here is what I say as to the boundaries between the intelligence of man and of animals. “Animals receive, through their senses, impressions similar to those that we receive through the medium of our senses; like ourselves, they retain the traces of these impressions: these impressions, when preserved, form for them, as well as for us, numerous and various associations: they combine them, they draw from them inferences, and deduce judgments from them: therefore they possess understanding.