There are five kinds of disease caused by various disorders on different planes of existence. Some diseases on the physical plane are contracted from without, while others spring from within. There are several supposed causes, but in reality the true cause of disease is weakness, while the cause of health is strength. This does not mean physical weakness or strength only, but strength and weakness on all planes of existence. Activity causes what is called life, while the reverse brings about death, the former causes circulation and the latter congestion. Circulation gives health, while congestion causes disease.