Quote: (maybe) Aristotle
It is the mark of an educated mind to be able to entertain a thought without accepting it.
Indeed it is. But I cannot find a source for the quote. It is listed as unsourced on Wikiquote (which is a pretty good indication of it being a misquotation). A google search does not reveal a source but only the usual suspects, that is, sites that spread quotations with no regard for their sources. Kennehtamy thinks that it is Aristotle but I couldn't find it by searching through neither Politics or Ethics on Gutenberg.