In the spirit and true sense of the word, no real scientist will be able to find a contradiction between his science built upon the facts of the sense world and the method by which the supersensible world is investigated. The scientist makes use of certain instruments and methods. He produces his instruments by transforming what “nature” offers him. The supersensible method of knowledge also makes use of an instrument. This instrument is man himself. This instrument, too, must first be made ready for higher research. The capacities and forces given to man by nature, without his assistance, must be transformed into higher capacities and powers. Man is thereby able to make himself the instrument for research in the supersensible world.
Source: Rudolf Steiner – GA 13 – An Outline of Occult Science – 1. The Character of Occult Science
Translated by Maud and Henry B. Monges and revised for this edition by Lisa D. Monges.