It may be well, also, to distinguish between the causes and motives of migration. Motives are subjective feelings existing within the individual which inspire his actions. They are the immediate forces which lead to movement, and may be divided into the same two general classes as causes. Causes are objective forces or conditions existing outside of the individual, which react upon him. They may exist in the physical environment or in the human environment, and operate by arousing motives, which in turn are the immediate springs of conduct. Since human nature is everywhere enough alike so that similar causes arouse similar motives, and since motives can hardly arise without some exterior cause, in our search for the origins of migratory movements it will ordinarily be sufficient to examine merely the causes. Thus in almost every case of migration we are justified in looking for some cause of a repellent nature, some dissatisfaction, disability, discontent, hardship, or other disturbing condition.[3] These discomforts may arise in any of the various interests of human life, and may be classified according to almost any classification which will include those interests. Probably the most satisfactory is the familiar one of Economic, Political, Social, and Religious. The economic causes of migrations are the earliest and by far the most important. They arise in connection with man’s efforts to make his living, and concern all interests which are connected with his productive efforts. They are disabilities or handicaps which affect his pursuit of food, clothing, and shelter, as well as the less necessary comforts of life. These are vital interests, and any dissatisfaction connected with them is of great weight with men.