In the idea of the original Fall, that of Lucifer, we must assume that the angels were created with both free-will and imperfect knowledge. These while not necessarily the same are concomitant. Lucifer acted on an error of judgement about the nature of the Self. Bridging a gap in knowledge in one of two possible ways he chose the wrong one - as, following him, did a substantial portion of the angelic host - in fact a definite proportion of that host, sometimes given as one tenth. Presumably God could have tweaked the parameter dictating the nature of this gap so that a different proportion could have resulted - up to one half? Or maybe even more if their ignorance was greater. Was there an optimisation or a trade-off that dictated the setting? This mythologem seems to anticipate the idea of a fundamental probabilistic uncertainty at the heart of creation, a collapse of the angelic wave-function. Whatever the stuff of reality it follows that it is measurable. Also, once this choice is made by the individual angels it is irrevocable. The angels who did not fall are not always poised at the brink of the same choice, so that in any period of time a similar proportion of unfallen angels would proceed to fall - it was a one-off choice. The latter case would seem to have been true of Adam and Eve: the longer they spent in paradise the higher the probability that they would transgress, so that their ruin would have probability of one in the long term.