We are also inclined to deprecate habits on the ground that the man in the grip of habit is hopelessly in the _*rut_, that the man who has reduced his work to habit ceases to be original and is incapable of further improvement. On the contrary, the grip of habit is but a support. The editor could not write his trenchant editorials, and the advertiser could not write his compelling copy, unless in the act of writing each could turn over to habit the manipulation of the pen, the formation of the letters, and the spelling of the words. The attorney cannot make his most logical arguments and the salesman cannot make the best presentation of his goods, unless they can depend upon habit for correct verbal expressions, unless their thoughts clothe themselves automatically in appropriate verbal forms. When we are in the grip of habit, if it be a good habit, we are not so much in a rut as on the steel rails where alone the greatest progress is <p 308> made possible. We are not enslaved by good habits, but rather might it be said that no man is truly free to advance and to make rapid progress till he has succeeded in establishing a mass of useful habits. HOW HABITS ARE FORMED Modern physiological psychology has dealt with the problem of explaining the possibility of the formation and maintenance of habits. The explanation is found in the mutual development of the mind and the nervous system and in the dependence of thought and action upon the nervous system, and particularly upon the brain. To understand habit we must look beyond thought and action and consider some of the fundamental characteristic features of the nervous system. One such characteristic is the plasticity of the nervous substance. If I bend a piece of paper and crease it, the crease will remain even after the paper is straightened out again. The paper is plastic, and plasticity means simply that the substance offers some resistance to adopting a <p 309> new form, but that when the new form is once impressed upon the substance it is retained. Some effort is required to overcome the plasticity of the paper and to form the crease, but when it is once formed the plasticity of the paper preserves the crease. Modern conceptions of psychology have emphasized the intimate relationship existing between our thoughts and our brains. Every time we think, a slight change takes place in the delicate nerve-cells in some part of the brain. Every action among these cells leaves its indelible mark, or crease. Just as it is easy for the paper to bend where it has been creased before, it is likewise easy for action to take place in the brain where it has taken place before.