The quoted passage is from Plato's Phaedo. Is it correct to group the sentence in boldface as "Then must (not existence) be revealed to her in thought, if at all?" ?
I think it means that Socrates asked, must the soul know nonexistence only by thought. Am I correct?
Then when does the soul attain truth?-for in attempting to consider anything in company with the body she is obviously deceived.
Yes, that is true.
Then must not existence be revealed to her in thought, if at all?
And thought is best when the mind is gathered into herself and none of these things trouble her-neither sounds nor sights nor pain nor any pleasure-when she has as little as possible to do with the body, and has no bodily sense or feeling, but is aspiring after being?