The greatest value of knowledge is that it can be communicated and retained. This makes it inestimably important for practice. Rational or abstract knowledge is that knowledge which is peculiar to the reason as distinguished from the understanding. The use of reason is that it substitutes abstract concepts for ideas of perception, and adopts them as the guide of action. The many-sided view of life which man, as distinguished from the lower animals, possesses through reason makes him stand to them as the captain, equipped with chart, compass and quadrant, and with a knowledge of navigation, stands to the ignorant sailors under his command.
Man lives two lives.
Besides his life in the concrete is his life in the abstract. In the former he struggles, suffers and dies as do the mere animal creatures. But in the abstract he quietly reflects on the plan of the universe as does a captain of a ship on the chart. He becomes in this abstract life of calm reasoning a deliberate observer of those elements which previously moved and agitated his emotions. Withdrawing into this serene contemplation, he is like an actor who has played a lively part on the stage and then withdraws and, as one of the audience, quietly looks on at other actors who are energetically performing.