The Master said, He who sets to work on a different strand destroys the whole fabric.

Confucius, Analects II.16

I doubt whether we are sufficiently attentive to the importance of elementary text-books.

"Verily, verily I say to you unless a grain of wheat falls into the earth and dies, it remains alone, but if it dies, it remains alone, but if it dies it bears much fruit. He who loves his life loses it." (Christian. John xii. 24,25.)