Interested in Language
1. I have known him (to) stay up all night working. (experience)
2. I know (that) he sometimes stays up working all night. (knowledge)
Could somebody develop on the first example (rephrase, give another example, explain)?
I was more concerned with the meaning (how sentence no.1 is different from sentence no. 2).
Know in the second example is a matter of 'knowledge', while in the the first one - a matter of experience. I do know how it's structured (have known sb (to) verb) but I don't fully grasp the idea behind the first, less common use.
1. From my experience, he was someone who stayed up at nights and worked.