Kepler, the great astronomer, grew wild as the mysteries of the stars unrolled before him. The teacher that half knows his subject will be cold and lifeless, but he whose soul has caught fire from the truths he carries glows with enthusiasm and knowledge and unconsciously inspires his students with his interests. Earnest feeling of truths clearly conceived is the secret of the enthusiasm so much admired and praised in a teacher. Common truths become transformed for such a teacher. His subject matter is so rich in radiant reality.
History becomes a common panorama.
Geography swells out into great continental stretches of nations and people. Astronomy becomes the march of worlds and world systems. When a teacher thoroughly knows his subject, is familiar with it, he has command of it. Knowledge thoroughly mastered gives a teacher command of the subject discussed. Instead of hurry and worry from a teacher who depends on the textbook to answer questions asked by students, the teacher is at home in his recitation.