Schopenhauer Passage Found
The Scowl of Minerva award goes to Dennis Mangan whose devotion to the texts of the Master has uncovered the place where he invokes Omnia mea mecum porto, albeit in altered word order:
Dear Dr. Vallicella,
I don't know if I'm doing this to death, but I did come across your motto, in Schopenhauer's Aphorisms on the Wisdom of Life, in Volume 1 of Parerga and Paralipomena, Chapter 5 (Counsels and maxims):
To be self-sufficient and to be all in all to oneself and to be able to say omnia mecum porto mea , is certainly the most useful qualification for our happiness. Hence Aristotle's saying [original Greek omitted] (felicitas sibi sufficientium est, Eudemian Ethics, VII. 2) ["Happiness belongs to those who are easily contented"] cannot be too often repeated. (It is also essentially the same idea that is expressed in that exceedingly well-turned sentence of Chamfort. I have prefixed it as a motto to this essay.) ["Happiness is no easy matter; it is very difficult to find it in ourselves and impossible to find it elsewhere."] For we cannot with any certainty count on anyone but ourselves; moreover, the difficulties and disadvantages, the dangers and annoyances, that society entails are countless and inevitable.
Please keep up the great blogging.