Moral Letters to Lucilius Section 19

Puta enim prudentiam esse; quomodo adsentietur oportet me ambulare? Hoc natura non recipit. Prudentia enim ei, cuius est, prospicit, non sibi. Nam nec ambulare potest nec sedere. Ergo adsensionem non habet, rationale animal non est. virtus si animal est, rationale est.

Car, admettons que la prudence soit un animal, comment se dira-t-elle, avec assentiment : « Il faut que je me promène ? »
Sa nature ne le comporte pas : car la prudence prévoit pour celui qui la possède, non pour elle. Elle ne peut ni se promener ni s’asseoir ; elle n’a donc pas d’assentiment, et qui n’en a pas n’est pas animal raisonnable. La vertu, si elle est animal, est raisonnable ;

For let us suppose that it is Prudence; how will Prudence assent to the opinion: “I must take a walk”? Nature does not allow this. For Prudence looks after the interests of its possessor, and not of its own self. Prudence cannot walk or be seated. Accordingly, it does not possess the power of assent, and it is not a living thing possessed of reason. But if virtue is a living thing, it is rational. But it is not rational; therefore it is not a living thing.