4. A habit is acquired by acts. Whereupon this difficulty has been started:--If the habit, say of mental application, comes from acts of study, and again the acts from the habit, how ever is the habit originally acquired? We answer that there are two ways in which one thing may come from another. It may come in point of its very existence, as child from parent; or in point of some mode of existence, as scholar from master. A habit has its very existence from acts preceding: but those acts have their existence independent of the habit. The acts which are elicited after the habit is formed, owe to the habit, not their existence, but the mode of their existence: that is to say, because of the habit the acts are now formed readily, reliably, and artistically, or virtuously. The primitive acts which gradually engendered the habit, were done with difficulty, fitfully, and with many failures,--more by good luck than good management, if it was a matter of skill, and by a special effort rather than as a thing of course, where it was question of moral well-doing. (See c.ii., s.ii., n.9, p. 10.) 5. A habit is a living thing: it grows and must be fed. It grows on acts, and acts are the food that sustain it. Unexercised, a habit pines away: corruption sets in and disintegration. A man, we will say, has a habit of thinking of God during his work. He gives over doing so. That means that he either takes to thinking of everything and nothing, or he takes up some definite line of thought to the exclusion of God. Either way there is a new formation to the gradual ruin of the old habit. 6. _Habit_ and _custom_ may be distinguished in philosophical language. We may say that custom makes the habit. Custom does not imply any skill or special facility. A habit is a channel whereby the energies flow, as otherwise they would not have flowed, freely and readily in some particular direction. A habit, then, is a determination of a faculty for good or for evil. It is something intrinsic in a man, a real modification of his being, abiding in him in the intervals between one occasion for its exercise and another: whereas custom is a mere denomination, expressive of frequent action and no more. Thus it would be more philosophical to speak of a _custom_ of early rising, and of a _custom_ of smoking, rather than of a _habit_ of smoking, except so far as, by the use of the word _habit_, you may wish to point to a certain acquired skill of the respiratory and facial muscles, and a certain acquired temper of the stomach, enabling one to inhale tobacco fumes with impunity.