What is the meaning of "knock into it" in this context?

Question

This is the context:

Paulson: Well, sort of the idea that somehow through the act of observation, we’re creating reality? Blockquote

Albert: Or yeah, or something like that. It’s true that you can only become sensually aware of stuff if, in one way or another, you knock into it. You might think that with enough work the knocking can be made as gentle as you would like, and it turns out to be a surprise, but something that’s true, that there are all kinds of circumstances in which the knocking can’t be made as gentle as you like. That’s a fact about the way the world is, but it is, as it were, a thoroughly understandable, mechanical fact about the way the world is. It was often interpreted to be something much more than that.

Source: The origins of the universe: why is there something rather than nothing? (in the Annals of The New York Academy Of Sciences)

Can anyone explains the bold part and specifically, the "knock into it" part?

Answer 1

It's a figurative use of:

verb (used without object)
 ..
 to strike in collision; bump: 
 _He knocked into a table._

(Dictionary.com)

the implication is that to become aware of "stuff" you have to (physically or at least mentally) "come into collision with it".