Two, or "2" as it's known to friends (or archaically: II), is the most important number.

It asserts 'an other' than one (1), and thereby implies all other numbers (and words, and languages, and possibilities) out to infinity.

Without 2, one cannot know itself or its environment. Two forces comparison, relationship, an acknowledgement and embracing of other-ness - and thus consciousness.

Without 2, we are left with binary zero-one, on-off, yes-no, alive-dead, endless non-conscious looping. Two breaks out of that paradigm.

Sadly, this theory makes the rest of the sentence (2 + 2 = ?) solveable, but irrelevant. In my opinion.