I'm currently reading Pierre Hadot book What is "Ancient Philosophy?" (Qu'est-ce que la philosophie antique?) and as I reach the third part of the book i can't stop thinking about, how exactly is ancient philosophy, understood by Hadot as a way of life, attached to a discourse, consecrated to the spirit, any different than religion in general? Specially given that many, if not all, of the philosophical schools discussed in the book, such as Platonism, Epicureanism or even Stoicism, do have some regard for assumed truths that rely on faith, specially in when it comes to the models of physics (not understood as a science but in the original greek sense of the word physis) it proposes.. Also, are they really different?
Note: I've seen a roughly "similar" question in the forum before however, as I contextualized my doubts in the body of the post, I expect a deeper answer than those given in the "similar" question I saw, preferentially given by someone familiar with the book I mentioned.