But that which is grounded to [proper] foundations does not wander around. [Non vagatur quod fixum atque fundatum est:] This is the blessed lot of the completely wise man, and also, to a certain extent, of him who is progressing and has made some headway. Now what is the difference between these two classes of men? The one is in motion, to be sure, but does not change its position; it merely tosses up and down where it is; the other is not in motion at all.--Seneca, Letter 35
In this very short letter, Seneca construes of teaching in terms of a proto-rational choice theory, as a kind of self-interested activity in which proper companions are cultivated ("When I urge you so strongly to your studies, it is my own interest which I am consulting.") In such a society of friends the benefit (or profit) is always mutual (itaque amicitia semper prodest). For Seneca this means that two minds become alike. What sustains the instructor's ongoing effort is the pleasure from imagining such an outcome (Ego quidem percipio iam fructum, cum mihi fingo uno nos animo futuros).
Seneca puts his cards on the table (recall this post for more reflection on the purposes behind this), like a magician who shows the mechanics of his trick before fooling you, again. For, Seneca, teaching involves the construction of the like minded out of course clay. This also acts as a kind of consolation against mortality--on this image a true student is the continuation of oneself (but, as we will be a bit clearer below), a self that is also radically non-individual.
This is an enduring idea, and, before one sees only narcissism in the image, it is worth noting that is connected to the idea of knowledge as consensus and that, say, experts speak in a single voice. Of course, for Seneca, the point is not that questions have one, and only one, true answer. The aim is rather, to shape, wills that are constant. This has (at least) two elements: first, he understands this construction as a progress toward what I call (recall here and here) integrity, that is "internal consistency" (ut constes tibi. ) Second, it requires steadfastness.
Now, when I first read the letter I assumed that he meant by this a lack of fickleness in one's goals--to have firm principles (the foundations) and well shaped ends. For Seneca clearly rejects fickleness in one's ends. But this misses the point.
Seneca is more radical here. I say this not to vindicate his position, but to give it its proper due. To be wise is the removal of oneself from the economy of unsteady desires and from responding to each and every incentive or stimulus. This ordinary economy of desire is one in which one is in continuous motion and running down of value. This idea is captured in an evocative passage in the Quran (103:2), Verily, man is in a state of loss. To have integrity and steadfastness means (see also 26:225) that one need not roam around. This can sound rather dull, but Seneca insists that the friendship of the wise involves a living pleasure (vivae voluptatis).