Whatever relates to their appetites strongly agitates their interior sense; and on the object of this appetite the dog would instantly rush, did not this very sense retain the impressions of pain which had formerly accompanied this action. By exterior impressions the animal has been modified. This prey is not presented to a dog simply, but to one which has been chastised every time it obeyed this impulse of appetite; the agitations of pain, therefore, are renewed when those of appetite are felt, having been constantly felt at the same time. The animal being thus impelled at once by two contrary powers, two powers destructive of each other, remains between them in an equilibrium; and, as the determinate cause of its motion is counterbalanced, it makes no effort to attain the object of its appetite. Though the agitations of appetite and repugnance, or of pleasure and pain, destroy the effect of each other, in the brain a third vibration takes place, which accompanies the other two, and this is occasioned by the action of its master, from whose hand the animal has often received its food; and as this is in no degree opposed or counterbalanced, it becomes the determinative cause of motion; and the dog is therefore determined to move towards its master, and to remain in motion till its appetite is entirely satisfied. In the same manner, and upon the same principles, may we explain, however complicated they appear, all the actions of animals, without allowing them either thought or reflection; the internal sense being sufficient to produce all their movements. The nature of their sensations alone remains to be elucidated, which, from what we have asserted, must be widely different from ours. "Have animals, it may be said, no knowledge, no consciousness of their existence? Do you deprive them of sentiment? In pretending to explain their actions upon mechanical principles, do you not in fact render them mere machines, or insensible automatons?" If I have been rightly understood, it must have appeared that, far from divesting animals of all powers, I allow them every thing, thought and reflection excepted. Feelings they have, in a degree superior to ourselves. A consciousness they also have of their present, though not of their past existence. They have sensations, but they have not the faculty of comparing them, or of producing ideas: ideas being nothing more than associations of sensations.