"Two powers govern the world," wrote Pope Gelasius, to the Greek
Emperor Anastasius, more than fourteen hundred years ago, "the
spiritual authority of the Roman Pontiff, and the temporal power of
kings". These two powers have for their end, one the spiritual
happiness of man, here and hereafter, the other the temporal
prosperity of society in the present world. So that, we may say,
speaking generally, the Roman Pontiff has, in spiritual and
ecclesiastical matters, the same authority that secular sovereigns and
their Parliaments have in worldly and political matters. They command
and issue laws not only as regards what is _necessary_ for the welfare
of their subjects, but also as regards whatever is lawful and
expedient. It is not contended that they never make a mistake. It is
not asserted that their ruling is necessarily, and in every
particular, always wise and discreet, but even inexpedient orders, if
not unjust, may be valid and binding, even though they might have been
better non-issued. The principle to guide us is of practical
simplicity. As regards both the Church and the State--each in its own
order--the rule is that obedience is to be yielded. And, in doubtful
cases the presumption is in favour of authority. If anything were
ordered, which is _clearly seen_ to be contrary to, or incompatible
with the Law of God, whether natural or revealed, then, of course, it
would possess no binding force, for the Apostle warns us that--"We
must obey God, rather than man"--but, so long as we remain in a state
of uncertainty, we are bound to give a properly constituted authority
the benefit of the doubt--and submit.

4. With these preliminary explanations and considerations to guide us
in our interpretation, we will now give the solemn teaching on the
subject, as laid down in the third chapter of the _Pastor Æternus_,
drawn up and duly promulgated by the Ecumenical Council of the