_Instinct_ and _reason_ are forms of intelligence. Intelligence is the adaptation of acts to ends. Intelligence is manifested by all organisms, both plants and animals, and may be either conscious or unconscious. Plant intelligence and reflex action are forms of _unconscious_ intelligence. Plant intelligence, or the adaptation of acts to ends by plants, is manifested by plants in the shifting of their positions when in need of light in order to obtain as large a supply as possible of the essential sunshine; in devices, such as traps and flowers, for utilising the juices and services of insects; in germinating and growing away from, instead of toward, the centre of the earth; in discriminating between this and that kind of food; and in a thousand other ways. Plant intelligence is all explicable in terms of chemistry and physics, and is, so far as is known, unaccompanied by consciousness. Reflex action is chemical affinity aided by the co-ordinating powers of nerve tissue. The vital processes of all animals, from the lowest to the highest, and many other highly habitual and highly essential operations, are carried on by reflex action. Reflex action in animals, like plant intelligence, is unconscious. Instinct and reason are _conscious_. Instinct is inherited intelligence—intelligence manifested independently of, and prior to, experience and instruction. ‘Instinct,’ says Romanes, ‘is reflex action into which has been imported the element of consciousness’.[5] It is exhibited by the babe when it nurses the mother’s breast; by the chick when it pecks its way out through the shell of the egg; by animals generally, including man, in their solicitude for their young; by the parent bird in incubation; and by all beings when they seek food in obedience to the impulse of hunger. Our conception of the mental processes of non-humans is as yet very primitive, owing to our limited means of information and the erroneous influence on our judgments of traditional ways of thinking; and much that is attributed by us to instinct is not instinct at all, but is acquired by the young through education imparted by the elders. Parent birds have often been seen teaching their young ones to fly, and no doubt a good deal of the migratory acumen manifested by birds is nothing but custom and tradition handed down to each younger generation by the old and experienced. A large part of the knowledge of mankind (or what passes for knowledge) consists of habits and hobbies, customs and traditions, impressed upon each new generation by the generation which produced it. Each generation of men seems to feel that whenever it creates a new generation it has got to pile on to this new generation all of the fool notions which have been acquired from the past, amplified by its own inventions. And when we come to know other animals better, there is practically no doubt that we shall find that a large part of what we now call instinct and look upon as congenital