Thomas Whately, in Observations on Modern Gardening, writes:
"In landscape gardening violations of unity are often to be met with, and they are always indicative of the absence of correct taste in art. Looking upon a landscape from the windows of a villa residence, we sometimes see a considerable portion of the view embraced by the eye laid out in natural groups of trees and shrubs, and upon one side, or, perhaps, in the middle of the same scene, a formal avenue leading directly up to the house. Such a view can never appear a satisfactory whole, because we experience a confusion of sensations in contemplating it. There is an evident incongruity in bringing two modes of arranging plantations, so totally different, under the eye at one moment, which distracts, rather than pleases the mind. In this example, the avenue, taken by itself, may be a beautiful object, and the groups and connected masses may, in themselves, be elegant, yet if the two portions are seen together, they will not form a whole, because they cannot make a composite idea. For the same reason, there is something unpleasing in the introduction of fruit trees among elegant ornamental trees on a lawn, or even in assembling together, in the same beds, flowering plants, and culinary vegetables—one class of vegetation suggesting the useful, and homely, alone to the mind, and the other, avowedly, only the ornamental.
"In the arrangement of a large extent of surface, where a great many objects are necessarily presented to the eye at once, the principle of unity will suggest that there should be some grand or leading features to which the others should be merely subordinate. Thus, in grouping trees, there should be some large and striking masses to which the others appear to belong, however distant, instead of scattered groups, all of the same size. Even in arranging walks, a whole will more readily be recognized, if there are one or two, of large size, with which the others appear connected as branches, than if all are equal in breadth, and present the same appearance to the eye in passing."
The difficulty with many landscape designs, whether the result of caprice, or of too strict adherence to the canons of a school, is that the plan selected is not really intelligent.
In the words of an acute and able writer, Harald Hoffding:
"Gradually man learns to substitute methods for systems and to ask how and how much in place of why. Instead of constructing the world according to the caprice of his imagination, he learns to discern the interconnection which actually obtains from it, and when in this way he gradually arrives at finding one great unity running through all things his imagination will regain in a more secure form all that it has lost when its daring pictures were crowded out by critical investigations."