central space open to the sky, became at a later time a roofed hall,
either, as in the case of the basilica at Trier, without aisles, or,
like the basilica of Maxentius or Constantine in the Roman forum, with a
series of deep recesses at the side, the vaulted roofs of which served
to counteract the outward pressure of the main vault. The Christian
basilica, if it were a mere imitation of this type of building, would
follow the same line of development; but, as a matter of fact, the
highest type of Christian church is always a colonnaded or aisled
building. And, even if the Christian apse derived its arrangement from
the apse or apses which projected from the ends or sides of the secular
basilicas, there is again a difference. The apse with its altar was the
main feature of the interior of the Christian church: it was the place
in which the chief rite of Christian worship was performed before the
eyes of all. In the secular basilica the apse was devoted to special
purposes which set it apart from the main business of the body of the
building: it was an appendage to the central hall, not necessarily
within view of every part of it. In fact, the relation of the apse to
the main building was totally different in the two cases.

Sec. 3. It seems probable, then, that the identity between the two
buildings is mainly an identity of name, and that Christian builders,
in seeking for suitable arrangements for public worship, may have
borrowed some details from the arrangements of the secular basilica. It
is natural, however, to look for the origin of a religious plan in
buildings devoted to religious purposes. The Roman temple supplied no
help for the plan of buildings which were required for public worship.
Of recent years, it has been customary to assume that the Christian
basilica took its form from the inner halls of the private houses of
those wealthy citizens who embraced Christianity in its early days. Such
halls may have been used for Christian services; and if their plan was
adopted for the Christian basilica, the mature state of the basilican
plan at its first appearance can be explained. The _atrium_ or entrance
hall of the house is represented on this hypothesis by the forecourt of
the basilica; the peristyle, or colonnade round the inner room, becomes
the aisles and the space screened off at the entrance for those not
entitled to take full part in the service; the colonnade at the further
end survives in the arcaded s