4 But you will perhaps say that the king was a diviner. Could he be more so than Jupiter himself? But for a mortal's anticipating what Jupiter— whom he overreached— was going to say, could the god not know in what ways a man was preparing to overreach him? Is it not, then, clear and manifest that these are puerile and fanciful inventions, by which, while a lively wit is assigned to Numa, the greatest want of foresight is imputed to Jupiter? For what shows so little foresight as to confess that you have been ensnared by the subtlety of a man's intellect, and while you are vexed at being deceived, to give way to the wishes of him who has overcome you, and to lay aside the means which you had proposed?
For if there was reason and some natural fitness that expiatory sacrifice for that which was struck with lightning should have been made with a man's head, I do not see why the proposal of an onion's was made by the king; but if it could be performed with an onion also, there was a greedy lust for human blood. And both parts are made to contradict themselves: so that, on the one hand, Numa is shown not to have wished to know what he did wish; and, on the other, Jupiter is shown to have been merciless, because he said that he wished expiation to be made with the heads of men, which could have been done by Numa with an onion's head.
Source: Against the Heathen (New Advent)