I would like today to draw your attention to the fact that on the border between the sensuous-visible world and the invisible-extrasensory world, indeed, a certain danger lies in wait for the human being, and that someone who wants to become an initiate has to overcome this danger at first. It consists in the fact that it is exceptionally difficult to distinguish illusion from reality, dreams from reality, vision from the real view at the border of the physical and the supraphysical worlds. In this area, it is very easy to confuse own fantastic things of the soul with the objective reality. One needs different qualities that are explained in the following: keeping cool, retaining certainty of the soul, courage, perseverance and energy at the border. If the human being lost the clearness about that which is appearance and what is reality at this border, he would have lost his mind, then he would be a fool instead of an initiate.
Nowadays an immense greed, a true fury exists with most people indeed, if they hear of such matters to behold something of the higher worlds. However, with most human beings the perseverance and the will and above all the strength to overcome everything that must remove the indicated dangers do not exist.
Source: Rudolf Steiner – GA 56 – Knowledge of Soul and Spirit: Lecture IV: Initiation – Berlin, 28 November 1907