We may observe the same effect of poetry in a lesser degree; and this is common both to poetry and madness, that the vivacity they bestow on the ideas is not derived from the particular situations or connexions of the objects of these ideas, but from the present temper and disposition of the person.  But how great soever the pitch may be, to which this vivacity rises, it is evident, that in poetry it never has the same feeling with that which arises in the mind, when we reason, though even upon the lowest species of probability.  The mind can easily distinguish betwixt the one and the other; and whatever emotion the poetical enthusiasm may give to the spirits, it is still the mere phantom of belief or persuasion.  The case is the same with the idea, as with the passion it occasions.  There is no passion of the human mind but what may arise from poetry; though at the same time the feelings of the passions are very different when excited by poetical fictions, from what they are when they are from belief and reality.  A passion, which is disagreeable in real life, may afford the highest entertainment in a tragedy, or epic poem.  In the latter case, it lies not with that weight upon us:  It feels less firm and solid:  And has no other than the agreeable effect of exciting the spirits, and rouzing the attention.  The difference in the passions is a clear proof of a like difference in those ideas, from which the passions are derived.  Where the vivacity arises from a customary conjunction with a present impression; though the imagination may not, in appearance, be so much moved; yet there is always something more forcible and real in its actions, than in the fervors of poetry and eloquence.  The force of our mental actions in this case, no more than in any other, is not to be measured by the apparent agitation of the mind.  A poetical description may have a more sensible effect on the fancy, than an historical narration.  It may collect more of those circumstances, that form a compleat image or picture.  It may seem to set the object before us in more lively colours.  But still the ideas it presents are different to the feeling from those, which arise from the memory and the judgment.  There is something weak and imperfect amidst all that seeming vehemence of thought and sentiment, which attends the fictions of poetry.

We shall afterwards have occasion to remark both the resemblance and differences betwixt a poetical enthusiasm, and a serious conviction.  In the mean time I cannot forbear observing, that the great difference in their feeling proceeds in some measure from reflection and general rules.  We observe, that the vigour of conception, which fictions receive from poetry and eloquence, is a circumstance merely accidental, of which every idea is equally susceptible; and that such fictions are connected with nothing that is real.  This observation makes us only lend ourselves, so to speak, to the fiction:  But causes the idea to feel very different from the eternal established persuasions founded on memory and custom.  They are somewhat of the same kind:  But the one is much inferior to the other, both in its causes and effects.