This turning to information given by another mind, whose sources of knowledge are beyond our own immediate reach, seems at first sight to be incompatible with the principles guiding all our studies hitherto; for in gaining insight into the How and Whence of a phenomenon of the sense-world we have up to now admitted only what is yielded by an observation of the phenomenon per se (though with the aid of the 'eye of the spirit') and of other phenomena related to it. This is what we have called 'reading in the book of nature', and we have found it to be the method on which a science aspiring to overcome the onlooker-picture of the universe must be based. So we must first make sure that the step we now propose to take does not violate this principle.