Nor will it be amiss to remark, that as a lively imagination very often degenerates into madness or folly, and bears it a great resemblance in its operations; so they influence the judgment after the same manner, and produce belief from the very same principles. When the imagination, from any extraordinary ferment of the blood and spirits, acquires such a vivacity as disorders all its powers and faculties, there is no means of distinguishing betwixt truth and falsehood; but every loose fiction or idea, having the same influence as the impressions of the memory, or the conclusions of the judgment, is received on the same footing, and operates with equal force on the passions. A present impression and a customary transition are now no longer necessary to enliven our ideas. Every chimera of the brain is as vivid and intense as any of those inferences, which we formerly dignified with the name of conclusions concerning matters of fact, and sometimes as the present impressions of the senses. 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 rise, 'tis 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, 'tis 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 arise 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 rousing 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 fervours 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