“ Animals are found susceptible of kindness, both to their own species and to ours ”
 David Hume, An Enquiry Concerning the Principles of Morals (1751). copy citation

Context

“how can we suppose, that his passionate tenderness arises from some metaphysical regards to a self-interest, which has no foundation or reality? We may as well imagine that minute wheels and springs, like those of a watch, give motion to a loaded waggon, as account for the origin of passion from such abstruse reflections. Animals are found susceptible of kindness, both to their own species and to ours; nor is there, in this case, the least suspicion of disguise or artifice. Shall we account for all THEIR sentiments, too, from refined deductions of self-interest? Or if we admit a disinterested benevolence in the inferior species, by what rule of analogy can we refuse it in the superior?” source