But it would be erroneous to conclude from all this that there cannot be any stable truths and dogmas, that progress to new and different views and doctrines is necessary. By the same right we might conclude that the main principles of the Copernican system cannot be immutable, because they would hinder the progress of science. Progress certainly does not consist in throwing away all certainty acquired, in order to begin anew. Or does it really belong to progress in astronomy to again give up _Copernicus_, to go back to _Ptolemy_ and let the sun and all the stars revolve again around the earth? Does not progress rather consist in our studying these astronomical results more closely, in building up the details, and, first of all, in trying to solve new problems? The champion of the faith will reply: Just as established results do not hinder the progress of science, just so do the doctrines of faith not form an obstacle to progress and evolution. The fixed doctrines of the faith themselves, in themselves and in their application to the conditions of life, offer rich material for the growth of religious knowledge. And there is the immense field for progress in the profane sciences. If any one should say that the believing scientist, who is bound by his dogmas, can do nothing further but reiterate his old truths, one might in turn argue: Then the astronomer bound by the fundamental rules of the Copernican system could have only the monotonous task of drawing over and over again the outlines of his system, while the mathematician who holds the multiplication table to be an unalienable possession would not be allowed to do aught but to repeat the multiplication table.