The other mode is by _changing the constitutional susceptibilities_. This can sometimes be effected to a certain degree by education and the formation of habits. It can be still more directly effected through the physical organization. For example, a child may be trained to use coffee, tea, alcohol, or tobacco, till the nervous system is shattered, and then a placid temper becomes excitable, a generous nature grows sour and selfish, an active nature becomes indolent, and multitudes of other disastrous changes are the result. These are the only two modes in which one mind is ever regarded as the cause of right or wrong volition in other minds. _On a Ruling Purpose._ The most important of all the voluntary phenomena is the fact that, while there can be a multitude of these quiet and hidden generic purposes in the mind, it is also possible to form _one_ which shall be the dominant or controlling one, to which all the other volitions, both generic and specific, shall become subordinate. In common parlance, this would be called the _ruling passion_. It may also be called the _ruling purpose_ or _controlling principle_. This consists in the permanent choice of some one mode of securing happiness as the _chief end_ or grand object of life. We have set forth on preceding pages the chief sources of happiness and of suffering to the human mind. Now in the history of our race we find that each one of these modes of enjoyment have been selected by different individuals as the chief end of their existence--as the mode of seeking enjoyment, to which they sacrifice every other. Some persons have chosen the pleasures of eating, drinking, and the other grosser enjoyments of sense. Others have chosen those more elevated and refined pleasures that come indirectly from the senses in the emotions of taste. Others have devoted themselves to intellectual enjoyments as their chief resource for happiness. Others have selected the exercise of physical and moral power, as in the case of conquerors and physical heroes, or of those who have sought to control by moral power, as rulers and statesmen. Others have made the attainment of the esteem, admiration, and love of their fellow-creatures their chief end. Others, still, have devoted themselves to the promotion of happiness around them as their chief interest. Others have devoted themselves to the service of God, or what they conceived to be such, and sometimes by the most miserable life of asceticism and self-torture. Others have made it their main object in life to obey the laws of rectitude and virtue. In all these cases, the _moral character_ of the person, in the view of all observers, has been decided by this dominant volition, and exactly in proportion to the supremacy with which it has _actually controlled_ all other purposes.