Moral Letters to Lucilius Section 12

Quid? Quod facienda quoque nemo rite obibit nisi is, cui ratio erit tradita, qua in quaque re omnes officiorum numeros exequi possit, quos non servabit, qui in rem praesentem praecepta acceperit, non in omnem. Inbecilla sunt per se et, ut ita dicam, sine radice, quae partibus dantur. Decreta sunt, quae muniant, quae securitatem nostram tranquillitatemque tueantur, quae totam vitam totamque rerum naturam simul contineant. Hoc interest inter decreta philosophiae et praecepta, quod inter elementa et membra; haec ex illis dependent, illa et horum causae sunt et omnium.

Et puis n’est-il pas vrai que nul ne fera bien ce qu’il doit faire, s’il n’est instruit par la raison à remplir en toute chose toute l’étendue de ses devoirs ? Celui-là ne les observera pas qui aura reçu des préceptes relatifs et non généraux. Toute leçon partielle est faible en elle-même et pour ainsi dire sans racine. Les axiomes seuls nous affermissent, nous maintiennent dans la sécurité et dans le calme, embrassent et la vie tout entière et toutes les lois de la nature. Il y a la même différence entre les axiomes de la philosophie et ses préceptes qu’entre les éléments et les corps : ceux-ci dépendent de ceux-là, ceux-là sont les causes de ceux-ci, comme de tout.

And why? Because no man can duly perform right actions except one who has been entrusted with reason, which will enable him, in all cases, to fulfil all the categories of duty. These categories he cannot observe unless he receives precepts for every occasion, and not for the present alone. Precepts by themselves are weak and, so to speak, rootless if they be assigned to the parts and not to the whole. It is the doctrines which will strengthen and support us in peace and calm, which will include simultaneously the whole of life and the universe in its completeness. There is the same difference between philosophical doctrines and precepts as there is between elements and members; the latter depend upon the former, while the former are the source both of the latter and of all things.