_Thirdly_, we have to deal with the historical stages of evolution, or the process within which works of art are executed in the various types and material. 1. THE SINGLE STATUE, THE GROUP AND THE RELIEF Just as, in the case of architecture, we made an essential distinction between independent building and that which was subservient we may also here establish a similar dividing line in sculpture, that is between such works that have an independent position and those which rather contribute to architectural decoration. In the case of the first the environment is nothing more than an artificially prepared locality, whereas in the latter cases their relation to the building which they adorn is of the first importance, and does not merely determine the form of the work of sculpture, but in a large measure even its content. Speaking in a summary way we may assert in this respect that single statues are set up on their own account, while groups and _a fortiori_ reliefs tend to lose this independence and are utilized by architecture for its own artistic purposes. (_a_) As to the single statue their original function is that of sculpture generally, that is to supply temple images as they are set up in the shrine of the temple, and all that surrounds them is in direct association with them. (_α_) In such a case sculpture retains its most adequate purity. It displays the figure of the god apart from all situation, in beautiful, unimpaired, and inactive tranquillity, or at least free, unmolested, without definite action and development, such as I have on several occasions depicted, that is, in unconstrained situations.