To discover beauties, or to point out faults, in the works of celebrated Masters, and to compare the conduct of one Artist with another, is certainly no mean or inconsiderable part of criticism; but this is still no more than to know the art through the Artist. This test of investigation must have two capital defects; it must be narrow, and it must be uncertain. To enlarge the boundaries of the Art of Painting, as well as to fix its principles, it will be necessary that _that_ art, and _those_ principles, should be considered in their correspondence with the principles of the other arts, which, like this, address themselves primarily and principally to the imagination. When those connected and kindred principles are brought together to be compared, another comparison will grow out of this; that is, the comparison of them all with those of human nature, from whence arts derive the materials upon which they are to produce their effects. When this comparison of art with art, and of all arts with the nature of man, is once made with success, our guiding lines are as well ascertained and established as they can be in matters of this description. This, as it is the highest style of criticism, is at the same time the soundest; for it refers to the eternal and immutable nature of things. You are not to imagine that I mean to open to you at large, or to recommend to your research, the whole of this vast field of science. It is certainly much above my faculties to reach it; and though it may not be above yours to comprehend it fully, if it were fully and properly brought before you, yet perhaps the most perfect criticism requires habits of speculation and abstraction, not very consistent with the employment which ought to occupy, and the habits of mind which ought to prevail, in a practical Artist. I only point out to you these things, that when you do criticise (as all who work on a plan will criticise more or less), your criticism may be built on the foundation of true principles; and that though you may not always travel a great way, the way that you do travel may be the right road. I observe, as a fundamental ground, common to all the Arts with which we have any concern in this discourse, that they address themselves only to two faculties of the mind--its imagination and its sensibility. All theories which attempt to direct or to control the Art, upon any principles falsely called rational, which we form to ourselves upon a supposition of what ought in reason to be the end or means of Art, independent of the known first effect produced by objects on the imagination, must be false and delusive. For though it may appear bold to say it, the imagination is here the residence of truth. If the imagination be affected, the conclusion is fairly drawn; if it be not affected, the reasoning is erroneous, because the end is not obtained; the effect itself being the test, and the only test, of the truth and efficacy of the means.