Reason -- this likewise is unreliable and not to be depended upon. This human world is an ocean of varying opinions. If reason is the perfect standard and criterion of knowledge, why are opinions at variance and why do philosophers disagree so completely with each other? This is a clear proof that human reason is not to be relied upon as an infallible criterion. For instance, great discoveries and announcements of former centuries are continually upset and discarded by the wise men of today. Mathematicians, astronomers, chemical scientists continually disprove and reject the conclusions of the ancients; nothing is fixed, nothing final; everything is continually changing because human reason is progressing along new roads of investigation and arriving at new conclusions every day. In the future much that is announced and accepted as true now will be rejected and disproved. And so it will continue ad infinitum.