Therefore, my Lucilius, do as you write to me that you are doing....
- Epistle 1
Stoic philosophy, especially in its Roman manifestation (which we find here in the works of Seneca), is unlike what many today would consider to be philosophy. It is not mere esoteric intellectualising, detached from reality, serving no practical purpose. Whatever intellectualising is done is ultimately for the sake of real world application. Philosophy has indeed been called ars vitae or the art of life. The very etymology of the word means the love [philo] of wisdom [sophia] in Greek. Wisdom is not wit, cleverness, or raw intelligence. It is correct understanding for knowing what to do and when to do it, with the aim of leading a life worth living. Of course, uncovering this understanding may take some very heavy intellectualising and vigorous thinking, but this is contemplation in the service of a practical end - living the good life. Wisdom, then, is an action. One cannot claim to have attained any measure of wisdom while his actions are out of tune with his intellect.
When Seneca urges his friend to do as he writes, these are not casual words. It is a subtle reminder that authentic philosophy is practised, not just talked about.