The question at hand and the topic of the letter is: can a wise man help another wise man. In Seneca's view, the answer is 'yes' for these reasons:
Each needs someone with whom he may make comparisons and investigations.
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The wise man also needs to have his virtues kept in action; and as he prompts himself to do things, so is he prompted by another wise man.
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He can quicken his impulses, and point out to him opportunities for honourable action. Besides, he can develop some of his own ideas; he can impart what he has discovered. For even in the case of the wise man something will always remain to discover, something towards which his mind may make new ventures.
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will bring joy to the other, he will strengthen his faith, and from the contemplation of their mutual tranquillity the delight of both will be increased. Moreover, they will communicate to each other a knowledge of certain facts; for the wise man is not all-knowing.
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the wise man cannot maintain his mental standard without intercourse with friends of his own kind – with whom he may share his goodness. 10. Moreover, there is a sort of mutual friendship among all the virtues.
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in order to prompt perfect reason, there is need of perfect reason.
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the wise man can also be useful by discussing honourable things in common, and by contributing his thoughts and ideas. Moreover, it is in accordance with Nature to show affection for our friends, and to rejoice in their advancement.
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Now virtue advises us to arrange the present well, to take thought regarding the future, to deliberate and apply our minds; and one who takes a friend into council with him, can more easily apply his mind and think out his problem.
Seneca closes the letter by musing that this sort of discussion (can the wise help the wise), is all simply "mental gymanstics." Seneca wants to discuss how to go about acting more like a wise person.
What good does this do me? Make me more brave now, more just, more restrained! I have not yet the opportunity to make use of my training ... teach me now what it is necessary for me to know!