I think the essence of it all is " time ", for ANYTHING to exist; it has to exist in time.......no time means nothing exists. So to say that before the big bang, there was no time; is to say NOTHING existed. That, in itself, is to ask the human mind to take on board something that is way beyond it's capabilities. To then ask it to theorise, on how the big bang could have come about; from a state of complete non being, a state where nothing existed to kick it into action, a state where no catalytic possibilities existed, a totally inert state........is to expect way too much. At the current moment in time, almost half the human race can't keep up with mental evolution at its current rate.........so best not to tax it too much !!