The best remedy for all these evils is exercise or _labor_; and labor is a surmounting of _difficulties_, an exertion of the contracting power of the muscles; and as such resembles pain, which consists in tension or contraction, in everything but degree.

Labor is not only requisite to preserve the coarser organs, in a state fit for their functions; but it is equally necessary to these finer and more delicate organs, on which, and by which, the imagination and perhaps the other mental powers act.

Since it is probable, that not only the inferior parts of the soul, as the passions are called, but the understanding itself makes use of some fine corporeal instruments in its operation; though what they are, and where they are, may be somewhat hard to settle: but that it does make use of such, appears from hence; that a long exercise of the mental powers induces a remarkable lassitude of the whole body; and on the other hand, that great bodily labor, or pain, weakens and sometimes actually destroys the mental faculties.

Now, as a due exercise is essential to the coarse muscular parts of the constitution, and that without this rousing they would become languid and diseased, the very same rule holds with regard to those finer parts we have mentioned; to have them in proper order, they must be shaken and worked to a proper degree.
SECTION VII.
EXERCISE NECESSARY FOR THE FINER ORGANS.
As common labor, which is a mode of pain, is the exercise of the grosser, a mode of terror is the exercise of the finer parts of the system; and if a certain mode of pain be of such a nature as to act upon the eye or the ear, as they are the most delicate organs, the affection approaches more nearly to that which has a mental cause.

In all these cases, if the pain and terror are so modified as not to be actually noxious; if the pain is not carried to violence, and the terror is not conversant about the present destruction of the person, as these emotions clear the parts, whether fine or gross, of a dangerous and troublesome incumbrance, they are capable of producing delight; not pleasure, but a sort of delightful horror, a sort of tranquillity tinged with terror; which, as it belongs to self-preservation, is one of the strongest of all the passions.