Preservation or destruction of a particular individual depends on the fact as to whether or no normal or pathological processes predominate in the total economy of the organism. This holds true of the fear instinct. The fear instinct is a delicate mechanism, and when its action is slightly intensified, the animal is on the way to destruction. For the cosmic forces are careless of the creatures which keep on pouring forth in generous profusion from the lap of nature. Living matter, or protoplasm can only exist under special, restricted conditions,--the least variation means death. The more complicated, and more organized protoplasm is, the more restricted are the conditions of its existence. A rise of a couple of degrees of temperature or a fall means disease and death. The same holds true of the rise and fall of quantity and quality of bodily secretion of glands and of other organs. Protoplasm can only exist in an _optimum_ environment. Any change spells disease and death. The fear instinct, being at the heart of highly organized life activities, is delicately responsive to any changes and variations from the _optimum_, requisite for the proper functioning of the organism. Any deviation from the _optimum_ environment, external or internal, produces corresponding changes in the fear instinct with consequent pathological changes in the organism. The fear instinct like a delicate indicator is the first to get deranged, with harmful results to the organism as a whole. We can thus realize the importance of keeping the fear instinct in good condition. We can understand the significance of Plato’s doctrine of rational guidance of the fear instinct. “What to fear and what not to fear” is at the basis of all organized life, individual and social.[3] FOOTNOTE: [3] See my work “The Source and Aim of Human Progress.” CHAPTER VI FEAR AND DISEASE If we examine closely the symptoms of fear, we invariably find the symptoms of functional psychosis or neurosis. Fear affects the muscular and sensory systems, the vasomotor system, the respiratory system, the sudorific glands, the viscera, the heart, the intestines, all organs and functions of the organism.