There are two points of departure to this later type. There is on the one hand _symbolic_ architecture, and on the other practical necessity and the _impulse of purpose_ to subserve that necessity. In the case of symbolical forms, as we have already had occasion to observe, architectonic purpose is merely an incidental feature, merely an external mode of co-ordination. The dwelling-house, on the contrary, erected as necessity itself, requires posts of wood, or just walls standing up straight with beams, which are laid across them at right angles, and a roofing, and constitutes, the other extreme. There can be no question that the necessity of this real and effective expediency makes its appearance as the result of its own demand. The distinction that may be raised, however, in answer to the question, whether genuine architecture--as we shall shortly have to consider it as the classic art of building--takes its rise solely in this necessity, or is to be deduced from independent and symbolical works, which conducted us of their own accord to buildings devoted to service, is the point in essential dispute. (_α_) It is the force of circumstances which brings to the fore forms in architecture which are wholly stamped with a useful purpose, and the abstract deductions of science, such as the rectilinear line, the right angle, and the smooth surface. For in serviceable architecture that which constitutes the real object, is, in its independence, as a statue, or more closely as human individuals, that is community, a people, brought together for objects of general significance, which no longer have as their aim the satisfaction of physical wants, but are such in a religious and political sense. In a special degree the need asserts itself to shape an enclosure for the image, the statue of the gods, or generally for that which is independently placed before us and actually present as sacred. Memnons, Sphinxes, and the like stand up in the open, or in a grove, that is in the external environment of nature. Images of this kind, however, and still more human images of gods, are borrowed from another realm than that of immediate Nature. They belong to the world of imagination, and come into existence through the artistic powers of mankind. The purely natural environment is therefore not sufficient; they require for their external frame a ground and an enclosure, which shall be derived from the same source as their own, in other words, such as are the product of the imagination, and have received their form by means of artistic effort. It is only in an environment created by art that the gods find themselves at home[67]. In such a case, however, this external frame does not possess its object in itself, but it subserves something other than itself, and is subject to the principle of purpose or expediency.