Before I leave for a 12-day holiday (yay!), I'd like to say a few words about Seneca.
I have finished reading the foreword, which was very useful in pointing out some of the main premises that all Greek and Roman philosophers shared, including Plato, Epicurus and Seneca. I may try to read Plato again with this knowledge. For the moment, I am halfway through the Letters to Lucilius. I bought the book and will take it with me on my trip
I think I have finally figured out why I enjoy reading Seneca, when reading Plato made me want to scream. It's not his ideas, although I agree with some of them, while I don't think I have met an idea of Plato's that I agree with (but maybe it's just me being pigheaded

). In fact, seen from this 21st century reader's point of view, Seneca probably had more in common with Plato than he has with any of my own views.
The big difference between Seneca and Plato is that Plato is trying to prove what he believes, and Seneca is trying to live according to what he believes. He isn't much interested in theory, and when he tries to convince, it's not about the theoretical principles of stoicism - he takes them for granted. It's about the need for a philosopher to live according to these principles, rather than simply paying them lip service.
This is just as well for me, because it spares me that ridiculous logic, based on false premises and misleading analogies, that I so hate in Plato, and that Seneca probably mostly agreed with. It also spares me from a complete review of Seneca's beliefs, most of which I know are untrue or just don't agree with.
What he does talk about is mostly things I can relate to: how so much of our already short lives are eaten up by claims from strangers that profit neither of us (the stranger or myself), for instance. How it's no use to complain about lack of time, when we keep wasting the time we do have. These things almost feel commonplace, and yet we spend all our life ignoring them.
I don't know, maybe I'm just reducing Seneca to a bunch of platitudes, but these platitudes speak to me much more than Plato's zany theories. I suppose Seneca may not have been very happy to see what I take away from his writings. On the other hand, as I mentioned at the beginning of this thread, it's amazing that I can find anything in common between myself and a Roman guy who lived 2000 years ago, had no need to work for a living, and had dozens of slaves to take care of his everyday needs (and of his vast capital)