Tusculan Disputations by Marcus Tullius Cicero

Neoptolemus, in Ennius, indeed, says that the study of philosophy was expedient for him, but that it required limiting to a few subjects, for that to give himself up entirely to it was what he did not approve of. And for my part, Brutus, I am perfectly persuaded that it is expedient for me to philosophize. For what can I do better, especially as I have no regular occupation? But I am not for limiting my philosophy to a few subjects, as he does. For philosophy is a matter in which it is difficult to acquire a little knowledge without acquainting yourself with many, or all its branches, nor can you well take a few subjects without selecting them out of a great number. Nor can anyone, who has acquired the knowledge of a few points, avoid endeavoring with the same eagerness to understand more.

But still, in a busy life, and in one mainly occupied with military matters, such as that of Neoptolemus was at that time, even that limited degree of acquaintance with philosophy may be of great use, and may yield fruit, not perhaps so plentiful as a thorough knowledge of the whole of philosophy, but yet such as in some degree may at times deliver us from the dominion of our desires, our sorrows, and our fears -- just as the effect of that discussion which we lately maintained in my Tusculan villa seemed to be that a great contempt of death was engendered, which contempt is of no small efficacy towards delivering the mind from fear; for whoever dreads what cannot be avoided can by no means live with a quiet and tranquil mind. But he who is under no fear of death, not only because it is a thing absolutely inevitable but also because he is persuaded that death itself has nothing terrible in it, provides himself with a very great resource towards a happy life.