We are conscious of the world round about us, because we have certain capacities and organs which enable us to perceive it. If we had other organs, this world would present an entirely different aspect. For example, if a man had no eyes enabling him to see the light, but an organ enabling him instead to perceive electricity, then he would not see this room flooded with light, but he would perceive electricity in every wire, flashing, streaming through it. — The world round about us, what we call our world, is therefore dependent upon our sense-organs.
Source: Rudolf Steiner – GA 100 – Theosophy and Rosicrucianism: Lecture IV: Man’s Further Destinies in the Spiritual Worlds – Kassel, 19th June 1907