DFF/clock necessity

Posted by Vfffzx on Jun 28, 2018; 11:35pm
URL: http://nand2tetris-questions-and-answers-forum.52.s1.nabble.com/DFF-clock-necessity-tp4032181.html

Hello and thanks for the book!
But clock explanation in this chapter is, imo, too superficial, and leaves too many questions:
1. Remembering something is time dependant - but why? If logisim doesn't lie to me, and i doubt it does, you can build bit gate without clock.
2. This is basically continuation of my first point: why dff is needed at all in bit gate, which works just fine without it?
3. "On the other hand, there is no difficulty in feeding the output of a sequential chip back into itself" - again, why? I don't see how you can feed output back without using additional gates like mux, and this can be done just as well with combinatorial chimps (also, i don't see relation between  two chips in figure 3.4: i'm pretty sure that if we pull that dff out of sequential chip, it (chip) will be combinatorial and will work).