The true initiate will never deny the facts found by scientific investigation, but will whole-heartedly acknowledge the truths and merits of science. He must refuse, however, to admit that the scientific dogmatist is capable of determining the limits of knowledge. The scientist is proud of understanding, in contrast to believing. But if it is here a question of believing and not believing, and the scientist is of the opinion that belief plays no part in the results of his researches, he is mistaken. It is simply impossible to investigate or to teach anything without believing.
Consider, for example, the cellular theory. In books we have very fine representations of cells, the division of the cells, the life of the cells, and so forth, clear and exact in every detail. But who among us has ever really seen this for himself with such distinctness? [please see note below] We all simply believe that it is so. Even the university professors, who teach these things, have in the rarest cases seen all this with their own eyes, and yet they lecture on it. They have not been able to see it for themselves, because things of this kind are both so difficult and so rarely possible to observe that only a few single individuals have succeeded in seeing them, and also because in reality they are by no means so clear and distinct as they appear in the pictures. […] But until he is able to see for himself, the scientist is obliged to believe, and the others with him. Yet he demands of spiritual science that no one shall believe, and that no one shall know more than himself.
Source: Rudolf Steiner – GA 109 – The Dedication of an Anthroposophical Group – Breslau, June 15, 1909
Please note that what applied to the cellular in 1909 now applies to molecular, nuclear or astronomical research.