As for that translation above from PD24, I would like to blame Bailey for it, but I have rarely if ever seen one by anyone else that makes for clear reading either.
Like Joshua said, the point in the end is not really so difficult but the wording is labyrinthine:
24. If you reject any single sensation, and fail to distinguish between the conclusion of opinion, as to the appearance awaiting confirmation, and that which is actually given by the sensation or feeling, or each intuitive apprehension of the mind, you will confound all other sensations, as well, with the same groundless opinion, so that you will reject every standard of judgment. And if among the mental images created by your opinion you affirm both that which awaits confirmation, and that which does not, you will not escape error, since you will have preserved the whole cause of doubt in every judgment between what is right and what is wrong.
We probably ought to work on a paraphrase!