Men aren’t yet mature enough for certain things. It would only have a harmful effect if one wanted to give them out. Even you, my brothers and sisters, couldn’t receive some of the highest truths. If I would tell you such a truth this room would be empty in a few minutes. Even people who have reached a certain stage in esoteric training can’t stand certain truths. And yet these are the very highest truths, and your training will eventually enable to you to receive them. But one who receives them too soon loses all support in life.
Imagine that a narrow plank is laid over a deep abyss. How many of you would be able to walk over it without getting dizzy? Certainly not all. But if someone painted a path as wide as this plank on the floor of a room it would be easy to walk along the strip without going off to the left or right. And yet he’s doing the same thing he’d have to do to walk the plank or strip on the ground.
The strip’s continuation is the physical world, the world of the senses. It gives men certainty, since it continually corrects wrong thoughts, feelings, etc. Now imagine that the physical world’s barriers had fallen so that a man really floats in air without outer support. This is an experience that everyone must go through at some point.
Source: Rudolf Steiner – GA 266 – ESOTERIC LESSONS I: Number 18 – Stuttgart, 9-15-1907