When, for any reason, nature takes away your hunger, go cheerfully on with your usual work, and do not eat until she gives it back. No matter if it is two, three, ten days, or longer; you may be perfectly sure that when it is time for you to eat you will be hungry; and if you are cheerfully confident and keep your faith in health, you will suffer from no weakness or discomfort caused by abstinence. When you are not hungry, you will feel stronger, happier, and more comfortable if you do not eat than you will if you do eat; no matter how long the fast. And if you live in the scientific way described in this book, you will never have to take long fasts; you will seldom miss a meal, and you will enjoy your meals more than ever before in your life. Get an earned hunger before you eat; and whenever you get an earned hunger, eat. CHAPTER XVII. A SUMMARY OF THE SCIENCE OF BEING WELL. Health is perfectly natural functioning, normal living. There is a Principle of Life in the universe; it is the Living Substance, from which all things are made. This Living Substance permeates, penetrates, and fills the interspaces of the universe. In its invisible state it is in and through all forms; and yet all forms are made of it. To illustrate: Suppose that a very fine and highly diffusible aqueous vapor should permeate and penetrate a block of ice. The ice is formed from living water, and is living water in form; while the vapor is also living water, unformed, permeating a form made from itself. This illustration will explain how Living Substance permeates all forms made from It; all life comes from It; it is all the life there is. This Universal Substance is a thinking substance, and takes the form of its thought. The thought of a form, held by it, creates the form; and the thought of a motion causes the motion. It cannot help thinking, and so is forever creating; and it must move on toward fuller and more complete expression of itself. This means toward more complete life and more perfect functioning; and that means toward perfect health. The power of the living substance must always be exerted toward perfect health; it is a force in all things making for perfect functioning. _All things are permeated by a power which makes for health._ _Man can relate himself to this power, and ally himself with it_; he can also separate himself from it in his thoughts. _Man is a form of this Living Substance, and has within him a Principle of Health._ This Principle of Health, when in full constructive activity, causes all the involuntary functions of man's body to be perfectly performed. _Man is a thinking substance, permeating a visible body, and the processes of his body are controlled by his thought._