It appears that the employment of columns connected with temples commenced, in Greece, in the manner observed upon the rock-cut tomb façades of Egypt and Lycia, and the chapels of Mesopotamia and Phœnicia: two columns were placed within the open front, between the projecting side walls; that is to say, the temple was _in antis_.
The next step was the removal of these side walls, or parastadæ, columns taking their place in the corners before them, and the _prostyle_ temple was thus obtained. These changes rendered several important alterations necessary. They caused a new wall to be erected before the interior of the cella, the naos, the colonnade of the front thus acquiring the nature of a portico, the pronaos. The jambs of the door in this wall were so inclined as to diminish the span of the lintel, the frame receiving upon its upper corners the stepped ears, or parotides, customary in Western Asia. A new member of the entablature was needed to replace the omitted wall and provide a bearing for the ceiling cross-beams--namely, the epistyle. It is possible that this member, distinctly separated, existed before the change, but it certainly was not necessary. The division of the cella into naos and pronaos finally altered the position of the front ceiling-beams; in the naos they lay, as before, resting upon the side walls, but in the pronaos they were placed lengthwise--from the columns to the newly erected division wall. Besides improving the construction of the portico ceiling, this greatly added to the beauty of the front entablature: epistyle and ceiling-beams would otherwise have lain upon each other, in the same direction, but from this change resulted the frieze of triglyphs and metopes upon the front, as upon the sides. The gain was not effected without a difficulty arising in the frieze above the end of the side wall and the corner column, the outer ceiling-beam of the pronaos thus lying in its length upon the epistyle without the formation of a metope. And here the constructive truth was first sacrificed in favor of the exterior appearance: a cube, standing above the corner column, took the place of the outer beam, and the continuous alternation of triglyphs and metopes was carried out.