You will never understand this unless you have investigated the actual standard by which such conditions are relatively rated. As leaves cannot flourish by their own efforts, but need a branch to which they may cling and from which they may draw sap, so your precepts, when taken alone, wither away; they must be grafted upon a school of philosophy. Moreover, those who do away with doctrines do not understand that these doctrines are proved by the very arguments through which they seem to disprove them. For what are these men saying? They are saying that precepts are sufficient to develop life, and that the doctrines of wisdom (in other words, dogmas) are superfluous. And yet this very utterance of theirs is a doctrine just as if I should now remark that one must dispense with precepts on the ground that they are superfluous, that one must make use of doctrines, and that our studies should be directed solely towards this end; thus, by my very statement that precepts should not be taken seriously, I should be uttering a precept. There are certain matters in philosophy which need admonition; there are others which need proof, and a great deal of proof, too, because they are complicated and can scarcely be made clear with the greatest care and the greatest dialectic skill. If proofs are necessary, so are doctrines; for doctrines deduce the truth by reasoning. Some matters are clear, and others are vague: those which the senses and the memory can embrace are clear; those which are outside their scope are vague.
But reason is not satisfied by obvious facts; its higher and nobler function is to deal with hidden things. Hidden things need proof; proof cannot come without doctrines; therefore, doctrines are necessary. That which leads to a general agreement, and likewise to a perfect one,838 is an assured belief in certain facts; but if, lacking this assurance, all things are adrift in our minds, then doctrines are indispensable; for they give to our minds the means of unswerving decision. Furthermore, when we advise a man to regard his friends as highly as himself, to reflect that an enemy may become a friend,839 to stimulate love in the friend, and to check hatred in the enemy, we add: “This is just and honourable.” Now the just and honourable element in our doctrines is embraced by reason; hence reason is necessary; for without it the doctrines cannot exist, either. But let us unite the two. For indeed branches are useless without their roots, and the roots themselves are strengthened by the growths which they have produced. Everyone can understand how useful the hands are; they obviously help us. But the heart, the source of the hands growth and power and motion, is hidden. And I can say the same thing about precepts: they are manifest, while the doctrines of wisdom are concealed. And as only the initiated840 know the more hallowed portion of the rites, so in philosophy the hidden truths are revealed only to those who are members and have been admitted to the sacred rites. But precepts and other such matters are familiar even to the uninitiated.
Posidonius holds that not only precept-giving (there is nothing to prevent my using this word), but even persuasion, consolation, and encouragement, are necessary. To these he adds the “investigation of causes” (but I fail to see why I should not dare to call it “aetiology,” since the scholars who mount guard over the Latin language thus use the term as having the right to do so). He remarks that it will also be useful to illustrate each particular virtue; this science Posidonius calls “ethology,” while others call it “characterization.”841 It gives the signs and marks which belong to each virtue and vice, so that by them distinction may be drawn between like things. Its function is the same as that of precept. For he who utters precepts says: “If you would have self-control, act thus and so!” He who illustrates, says “The man who acts thus and so, and refrains from certain other things, possesses self-control.” If you ask what
