People need instruction to align their actions with their knowledge of health principles.

Original passage

Many transgress the laws of health through ignorance, and they need instruction. But the greater number know better than they do. They need to be impressed with the importance of making their knowledge a guide of life. The physician has many opportunities both of imparting a knowledge of health principles and of showing the importance of putting them in practice. By right instruction he can do much to correct evils that are working untold harm.