"but are you saying here that if we can observe it directly it may be a confirmable truth"

No. The first part is the philosophical uncertainty (Kant, 1790's), and 2 is a psychophysical barrier to certainty (20th century) about perception. That quote just left out the second part of the story.

Thanks for asking!

Paul! You've picked up this stuff very quickly! Great work.

"I'm looking forward to participating in #higherorderthinking."

Membership is OPEN! C u there.