9 So, if some ox, or any animal you please, which is slain to mitigate and appease the fury of the deities, were to take a man's voice and speak these words: “Is this, then, O Jupiter, or whatever god you are, humane or right, or should it he considered at all just, that when another has sinned I should be killed, and that you should allow satisfaction to be made to you with my blood, although I never did you wrong, never wittingly or unwittingly did violence to your divinity and majesty, being, as you know, a dumb creature, not departing from the simplicity of my nature, nor inclined to be fickle in my manners? Did I ever celebrate your games with too little reverence and care? Did I drag forward a dancer so that your deity was offended? Did I swear falsely by you? Did I sacrilegiously steal your property and plunder your temples? Did I uproot the most sacred groves, or pollute and profane some hallowed places by rounding private houses? What, then, is the reason that the crime of another is atoned for with my blood, and that my life and innocence are made to pay for wickedness with which I have nothing to do? Is it because I am a base creature, and am not possessed of reason and wisdom, as these declare who call themselves men, and by their ferocity make themselves beasts? Did not the same nature both beget and form me from the same beginnings? Is it not one breath of life which sways both them and me? Do I not respire and see, and am I not affected by the other senses just as they are? They have livers, lungs, hearts, intestines, bellies; and do not I have as many members? They love their young, and come together to beget children; and do not I both take care to procure offspring, and delight in it when it has been begotten? But they have reason, and utter articulate sounds; and how do they know whether I do what I do for my own reasons, and whether that sound which I give forth is my kind of words, and is understood by us alone? Ask piety whether it is more just that I should be slain, that I should be killed, or that man should be pardoned and be safe from punishment for what he has done? Who formed iron into a sword? Was it not man? Who brought disaster upon races; who imposed slavery upon nations? Was it not man? Who mixed deadly draughts, and gave them to his parents, brothers, wives, friends? Was it not man? Who found out or devised so many forms of wickedness, that they can hardly be related in ten thousand chronicles of years, or even of days? Was it not man? Is not this, then, cruel, monstrous, and savage? Does it not seem to you, O Jupiter, unjust and barbarous that I should be killed, that I should be slain, that you may be soothed, and the guilty find impunity?”
It has been established that sacrifices are offered in vain for this purpose then, viz., that the angry deities may be soothed; since reason has taught us that the gods are not angry at any time, and that they do not wish one thing to be destroyed, to be slain for another, or offenses against themselves to be annulled by the blood of an innocent creature.
Source: Against the Heathen (New Advent)