I think that his point was that every event (everything which exists) is related to every other event. Some of these relations are distant and have little effect (unnoticeable effect) and some are obviously related (these are usually the only factors which are considered). Bucky wanted us to be aware of the fact that even the events which did not seem relevant to our question still had some relation (and maybe more significance than we would have guessed).

He decided that until he could answer the question "What is Universe?" he could not answer any other questions.