The characters of nature are legible, it is true; but they are not plain enough to enable those who run, to read them. We must make use of a cautious, I had almost said, a timorous method of proceeding. We must not attempt to fly, when we can scarcely pretend to creep. In considering any complex matter, we ought to examine every distinct ingredient in the composition, one by one; and reduce everything to the utmost simplicity; since the condition of our nature binds us to a strict law and very narrow limits. We ought afterwards to re-examine the principles by the effect of the composition, as well as the composition by that of the principles. We ought to compare our subject with things of a similar nature, and even with things of a contrary nature; for discoveries may be, and often are made by the contrast, which would escape us on the single view. The greater number of the comparisons we make, the more general and the more certain our knowledge is likely to prove, as built upon a more extensive and perfect induction. If an inquiry thus carefully conducted should fail at last of discovering the truth, it may answer an end perhaps as useful, in discovering to us the weakness of our own understanding. If it does not make us knowing, it may make us modest. If it does not preserve us from error, it may at least from the spirit of error; and may make us cautious of pronouncing with positiveness or with haste, when so much labor may end in so much uncertainty. I could wish that, in examining this theory, the same method were pursued which I endeavored to observe in forming it. The objections, in my opinion, ought to be proposed, either to the several principles as they are distinctly considered, or to the justness of the conclusion which is drawn from them. But it is common to pass over both the premises and conclusion in silence, and to produce, as an objection, some poetical passage which does not seem easily accounted for upon the principles I endeavor to establish. This manner of proceeding I should think very improper. The task would be infinite, if we could establish no principle until we had previously unravelled the complex texture of every image or description to be found in poets and orators. And though we should never be able to reconcile the effect of such images to our principles, this can never overturn the theory itself, whilst it is founded on certain and indisputable facts. A theory founded on experiment, and not assumed, is always good for so much as it explains. Our inability to push it indefinitely is no argument at all against it. This inability may be owing to our ignorance of some necessary _mediums_; to a want of proper application; to many other causes besides a defect in the principles we employ. In reality, the subject requires a much closer attention than we dare claim from our manner of treating it.