[...] What do you mean by provoking me like this with your "architect"? Can't you see that all our plastic arts derive from architecture and are parts of the same? In the architect, simple human necessity (the need of a dwelling-place in the first instance) becomes the begetter of an artistic design, just as with the poet artistic intent grows out of the need of life. To carry out his intent the architect needs the aid of the sculptor and the painter to give his mathematical straight lines, angles and corners as far as possible the non-arbitrary formation of free nature. Nevertheless—but I can't express my meaning so briefly. Only this much more—the architect is in immediate contact with life's necessities—the architect (the constructor of naked form) is the prime mover not only in the making of the house, but of every bench, table and chest. He is inspired finally to his highest artistic work by the highest of human needs, and that is the poetic. Here, then, he comes into immediate contact with the poet, but up till then he grows independently out of the soil of life. I know nothing of any absolutely independent architectural work of art, unconditioned either by the needs of ordinary life or by poetic needs, though King Ludwig of Bavaria may. Such a work of art can only be based on imitation, namely on the imitation of architectonic works of art which in other times and under other conditions answered to a real, if exaggerated and luxurious need. But the Greek temple was in its time an actual religious necessity to the Hellenes, and not less so were the churches of the Middle Ages, etc. All these arose out of what was almost an artistic necessity of their periods. In the future we shall only have the theatre instead, because our highest artistic need can no longer be of an ecclesiastically-religious, nor of a princely and luxurious, nature. I recognise no absolute work of art at all, and therefore no absolute work of architectural art.
Another time, spare me this sort of learned rubbish!—[...]
Source: Letters of Richard Wagner, Vol. 1, selected and ed. Wilhelm Altmann, trans. M. M. Bozman (J. M. Dent & Sons, 1927), No. 212