Sense, therefore, and not intelligence, is the regulatory principle of instinct. To recognize causal and telic relationships is the prerogative of a superorganic intelligence. The transcendental link by which a useful means is referred to an ulterior end is something that cannot be _sensed_, but only _understood_. An animal, therefore, acts _toward_ an end, not _on account of_ an end. Nature, however, has compensated for this ignorance by implanting in each species of animal a special teleological disposition, by reason of which objects and actions, which are, under normal conditions, objectively useful to the individual, or the species, become invested for the animal with a subjective aspect of agreeableness, while objects and actions, which are normally harmful, are invested with a subjective aspect of repulsiveness. The qualities of serviceableness and pleasantness _happen_, so far as the animal is concerned, to be united in one and the same concrete object or action, but the animal is only aware of the pleasantness, which appeals to its senses, and not of the serviceableness, which does not. Thus, in the example already cited, the dog suffering from tapeworms eats the herb known as Common Wormwood, not because it is aware of the remedial efficacy of the herb, but simply because the odor and flavor of the plant appeal to the animal in its actual morbid condition, ceasing to do so, however, when the latter regains the state of health. How different is the action of the man whose blood is infected with malarial parasites and who takes quinine, not because the bitter taste of the alkaloid appeals to his palate, but solely because he has his future cure explicitly in view! “Finally,” says Weld, “the more we learn about instincts the more apparent it becomes that the situations from which they proceed are meaningful, but we need not suppose that the organism is aware of the meaning. The chick in the egg feels (we may only guess as to its nature) a vague discomfort, and the complicated reaction by which it makes its egress from the shell is released.” (Encycl. Am., v. 15, p. 169.) Recapitulating, then, we may define instinct as a psycho-organic propensity, not acquired by education or experience, but congenital by inheritance and identical in all members of the same zoölogical species, having as its physical basis the specific nervous organization of the animal and as its psychic basis a teleological coördination of the cognitive, emotional, and motor functions, in virtue of which, given the proper physiological state of the organism and the presence of an appropriate environmental stimulus, an animal, without consciousness of purpose, is impelled to the inception, and regulated in the performance, of complicated behavior which is sensually gratifying and, under normal circumstances, simultaneously beneficial to the individual, or the race.