But how full of trouble and contradiction in respect of one another these things are, what need is there to say at present? But the reputation of Arcesilaus, who was the best beloved and most esteemed of all the philosophers in his time, seems to have been no small eyesore to Epicurus; who says of him that, delivering nothing peculiar to himself or of his own invention, he imprinted in illiterate men an opinion and esteem of his being very knowing and learned. Now Arcesilaus was so far from desiring any glory by being a bringer-in of new opinions, and from arrogating to himself those of the ancients, that the sophisters of that time blamed him for attributing to Socrates, Plato, Parmenides, and Heraclitus the doctrines concerning the retention of assent, and the incomprehensibility of things; having no need so to do, but only that he might strengthen them and render them recommendable by ascribing them to such illustrious personages. For this therefore thanks to Colotes, and to every one who declares that the Academic doctrine was from higher times derived to Arcesilaus. Now as for the retention of assent and the doubting of all things, not even those who have much labored in the matter, and strained themselves to compose great books and large treatises concerning it, were ever able to stir it; but bringing at last out of the Stoa itself the cessation from all actions, as the Gorgon to frighten away the objections that came against them, they were at last quite tired and gave over. For they could not, what attempts and stirs soever they made, obtain so much from the instinct by which the appetite is moved to act, as to suffer itself to be called an assent, or to acknowledge sense for the origin and principle of its propension, but it appeared of its own accord to present itself to act, as having no need to be joined with any thing else. For against such adversaries the combat and dispute is lawful and just. And Such words as you have spoke, the like you may Expect to hear. For to speak to Colotes of instinct and consent is, I suppose, all one as to play on the harp before an ass. But to those who can give ear and conceive, it is said that there are in the soul three sorts of motions, — the imaginative, the appetitive, and the consenting. As to the imaginative or the apprehension, it cannot be taken away, though one would. For one cannot, when things approach, avoid being informed and (as it were) moulded by them, and receiving an impression from them. The appetite, being stirred up by the imaginative, effectually moves man to that which is proper and agreeable to his nature, just as when there is made a propension and inclination in the principal and reasonable part. Now those who withhold their assent and doubt of all things take not away this, but make use of the appetition or instinct naturally conducting every man to that which seems convenient for him. What then is the only thing that they shun? That in which is bred falsehood and deceit, — that is, opining, and precipitation in giving consent, — which is a yielding through weakness to that which appears, and has not any true utility. For action stands in need of two things, to wit, the apprehension or imagination of what is agreeable to Nature, and the instinct or appetition driving to that which is so imagined; of which, neither the one nor the other is repugnant to the retention of assent. For reason withdraws us from opinion, and not from appetition or imagination. When therefore that which is delectable seems to us to be proper for us, there is no need of opinion to move and carry us to it, but appetition immediately exerts itself, which is nothing else but the motion and inclination of the soul.