Earlier quoted context omitted.
What if when jumping off a roof, I spontaneously developed the ability to fly? And yet I will not attempt it, and worse, strongly evangelize that roofhopping should be avoided by everyone. How arrogant of me, how presumptuous! Though we cannot tell in every case what the outcome will be, that is no excuse to not consider the odds.
But lots of people did jump off of things with various contraptions and we did eventually develop the ability to fly that way.
These people after all pursued theoretical means by which the risk of death could be reduced, and then put them into practice in order to improve their understanding.
You can die in the air. You can die on the ground! Sometimes jumping off a cliff is safer than staying there. There is no safe path, no guarantee of survival; you have to speculate, to make theories, to test them, to choose the path that seems best to you. There is nothing arrogant about this.