Ante-Nicene Fathers, Vol VII:
Lactantius: Chap. XXXV.—That immortality is the chief good

Chap. XXXV.—That Immortality is the Chief Good.

What, then, will be the advantage of justice and virtue, if they shall have nothing but evil in life? But if virtue, which despises all earthly goods, most wisely endures all evils, and endures death itself in the discharge of duty, cannot be without a reward, what remains but that immortality alone is its reward? For if a happy life falls to the lot of man, as the philosophers will have it, and in this point alone they do not disagree, therefore also immortality falls to him. For that only is happy which is incorruptible; that only is incorruptible which is eternal. Therefore immortality is the chief good, because it belongs both to man, and to the soul, and to virtue. We are only directed to this; we are born to the attainment of this. Therefore God proposes to us virtue and justice, that we may obtain that eternal reward for our labours. But concerning that immortality 1498 itself we will speak in the proper place. There remains the philosophy of Logic, 1499 which contributes nothing to a happy life. For wisdom does not consist in the arrangement of speech, but in the heart and the feeling. But if natural philosophy is superfluous, and this of logic, and the philosophers have erred in moral philosophy, which alone is necessary, because they have been unable in any way to find out the chief good; therefore all philosophy is found to be empty and useless, which was unable to comprehend the nature of man, or to fulfil its duty and office.  

Footnotes

Non mortalitate.  

λογικὴ, philosophia. Under this is included everything connected with the system of speaking.