3rd Century Neo-Platonic mystic named Plotinus.

Even if it wasn’t truly observed by me because I am not the observer, even if the contents of the experience had no more truth than a dream, even if each effort to do so quickly passed out of view, it happened. And that is how I also realized that in happening, these experiences existed. Try falsifying experience for yourself and see if the experience of attempting it doesn’t arise, contradicting your effort.