'Tis certain, that sympathy is not always limited to the present moment, but that we often feel, by communication, the pains and pleasures of others which are not in being, and which we only anticipate by the force of imagination. For, supposing I saw a person perfectly unknown to me, who, while asleep in the fields, was in danger of being trod under foot by horses, I should immediately run to his assistance; and in this I should be actuated by the same principle of sympathy which makes me concerned for the present sorrows of a stranger. The bare mention of this is sufficient. Sympathy being nothing but a lively idea converted into an impression, 'tis evident that, in considering the future possible or probable condition of any person, we may enter into it with so vivid a conception as to make it our own concern, and by that means be sensible of pains and pleasures which neither belong to ourselves, nor at the present instant have any real existence. But however we may look forward to the future in sympathizing with any person, the extending of our sympathy depends in a great measure upon our sense of his present condition. 'Tis a great effort of imagination to form such lively ideas even of the present sentiments of others as to feel these very sentiments; but 'tis impossible we could extend this sympathy to the future without being aided by some circumstance in the present, which strikes upon us in a lively manner. When the present misery of another has any strong influence upon me, the vivacity of the conception is not confined merely to its immediate object, but diffuses its influence over all the related ideas, and gives me a lively notion of all the circumstances of that person, whether past, present, or future; possible, probable, or certain. By means of this lively notion I am interested in them, take part with them, and feel a sympathetic motion in my breast, conformable to whatever I imagine in his. If I diminish the vivacity of the first conception, I diminish that of the related ideas; as pipes can convey no more water than what arises at the fountain. By this diminution I destroy the future prospect which is necessary to interest me perfectly in the fortune of another. I may feel the present impression, but carry my sympathy no farther, and never transfuse the force of the first conception into my ideas of the related objects. If it be another's misery which is presented in this feeble manner, I receive it by communication, and am affected with all the passions related to it: but as I am not so much interested as to concern myself in his good fortune as well as his bad, I never feel the extensive sympathy, nor the passions related to _it_.