Thanks to his insight into the supersensible world, the initiate gains a better knowledge and appreciation of the true value of visible nature than was possible before his higher training; and this may be counted among his most important experiences. Anyone not possessing this insight and perhaps therefore imagining the supersensible regions to be infinitely more valuable, is likely to underestimate the physical world. Yet the possessor of this insight knows that without experience in visible reality he would be totally powerless in that other invisible reality. Before he can live in the latter he must have the requisite faculties and instruments which can only be acquired in the visible world. Consciousness in the invisible world is not possible without spiritual sight, but this power of vision in the higher world is gradually developed through experience in the lower. No one can be born in the spiritual world with spiritual eyes without having first developed them in the physical world, any more than a child could be born with physical eyes, had they not already been formed within the mother’s womb.
Source; Rudolf Steiner – GA 10 – Knowledge of the Higher Worlds: XI: Life and Death: The Greater Guardian of the Threshold
Translated by George Metaxa