From "A Dissertation on the Duty of Mercy and Sin of Cruelty to Brute Animals" by Humphrey Primatt, ca.1735-ca.1777
However men may differ as to speculative points of religion, justice is a rule of universal extent and invariable obligation. We acknowledge this important truth in all matters in which man is concerned, but then we limit it to our own species only. And though we are able to trace the most evident marks of the Creator’s wisdom and goodness in the formation and appointment of the various classes of animals that are inferior to men, yet the consciousness of our own dignity and excelence is apt to suggest to us, that man alone of all terrestrial animals is the only proper object of mercy and compassion, because he is the most highly favoured and distinguished. Misled with this prejudice in our own favour, we overlook some of the brutes, as if they were mere excrescences of nature, beneath our notice and infinitely unworthy the care and cognisance of the Almighty and we consider others of them as made only for our service and so long as we can apply them to our use, we are careless and indifferent as to their happiness or misery, and can hardly bring our selves to suppose that there is any kind of duty incumbent upon us toward them.
To rectify this mistaken notion is the design of this treatise, in which I have endeavoured to prove, that as the love and mercy of God are over all of his works, from the highest rational to the lowest sensitive, our love and mercy are not to be confined within the circle of our own friends, acquaintance and neighbours; nor limited to the more enlarged sphere of human nature, to creatures of our own rank, shape and capacity; but are to be extended to every object of the love and mercy of God the universal parent; who, as he is righteous in all his ways, and holy in all his works, will undoubtedly require of man, superior man, a strict account of his conduct to every creature entrusted to his care, or coming in his way and who will avenge every instance of wanton cruelty and oppression, in the day in which he will judge the world in righteousness.