This power which nature hath given us over our train of perceptions, may be greatly strengthened by proper discipline, and by an early application to business. Its improved strength is remarkable in those who have a strong genius for the mathematics: nor less remarkable in persons devoted to religious exercises, who pass whole days in contemplation, and impose upon themselves long and severe penances. It is not to be conceived, what length a habit of activity in affairs will carry some men. Let a stranger, or let any person to whom the sight is not familiar, attend the Chancellor of Great Britain through the labours but of one day, during a session of parliament: how great will be his astonishment! what multiplicity of law-business, what deep thinking, and what elaborate application to matters of government! The train of perceptions must in this great man be accelerated far beyond the common course of nature. Yet no confusion nor hurry; but in every article the greatest order and accuracy. Such is the force of habit! How happy is man, to have the command of a principle of action, that can elevate him so far above the ordinary condition of humanity[95]! We are now ripe for considering a train of perceptions with respect to pleasure and pain: and to this speculation we must give peculiar attention, because it serves to explain the effects that uniformity and variety have upon the mind. A man is always in a pleasant state of mind, when his perceptions flow in their natural course. He feels himself free, light, and easy, especially after any forcible acceleration or retardation. On the other hand, the resistance felt in retarding or accelerating the natural course, excites a pain, which, though scarcely felt in small removes, becomes considerable toward the extremes. An aversion to fix on any single object for a long time, or to take in a multiplicity of objects in a short time, is remarkable in children; and equally so in men unaccustomed to business. A man languishes when the succession is very slow; and, if he grow not impatient, is apt to fall asleep. During a rapid succession, he hath a feeling as if his head were turning round. He is fatigued, and his pain resembles that of weariness after bodily labour. External objects, when they occasion a very slow or a very quick succession, produce a pain of the same sort with what it felt in a voluntary retardation or acceleration: which shows that the pain proceeds not from the violence of the action, but from the retardation or acceleration itself, disturbing that free and easy course of succession which is naturally pleasant.