From that day Rome entered upon the acute stage of her decline, and she
did so very largely because Marcus Aurelius, the ideal stoic, was
incapable of violating the great law of nature which impelled him to
follow not reason, but the path of least resistance in choosing a
successor; or, in other words, the instinct of heredity. Moreover, this
instinct and not reason is or has been, among the strongest which operate
upon men, and makes them automata. It is the basis upon which the family
rests, and the family is the essence of social cohesion. Also the
hereditary instinct has been the prime motor which has created
constructive municipal jurisprudence and which has evolved religion.

With the death of Marcus Aurelius individual competition may be judged to
have done its work, and presently, as the population changed its character
under the stress thereof, a new phase opened: a phase which is marked, as
such phases usually are, by victory in war. Marcus Aurelius died in 180
A.D. Substantially a century later, in 312, Constantine won the battle of
the Milvian Bridge with his troops fighting under the Labarum, a standard
bearing a cross with the device "_In hoc signo vinces_"; By this sign
conquer. Probably Constantine had himself scanty faith in the Labarum, but
he speculated upon it as a means to arouse enthusiasm in his men. It
served his purpose, and finding the step he had taken on the whole
satisfactory, he followed it up by accepting baptism in 337 A.D.

From this time forward the theory of the possibility of securing divine or
supernatural aid by various forms of incantation or prayer gained steadily
in power for about eight centuries, until at length it became a passion
and gave birth to a school of optimism, the most overwhelming and the most
brilliant which the world has ever known and which evolved an age whose
end we still await.