Encyclical of Pope Leo XIII On the Unity of the Church, 29 June 1896
Abridged from sections 2 through 10.
As in the natural order God does not usually give full perfection except by means of
man's work and action, so also He makes use of human aid for that which lies beyond the
limits of nature, that is to say, for the sanctification and salvation of souls.
And, since it was necessary that His divine mission should be perpetuated to the end of
time, He took to Himself Disciples, trained by himself, and made them partakers of His own
authority. He bade them go through the whole world and faithfully preach to all nations,
what He had taught and what He had commanded, so that by the profession of His doctrine,
and the observance of His laws, the human race might attain to holiness on earth and
neverending happiness in Heaven. In this wise, and on this principle, the Church was
begotten. If we consider the chief end of His Church and the proximate efficient causes of
salvation, it is undoubtedly spiritual; but in regard to those who constitute it,
and to the things which lead to these spiritual gifts, it is external and
Jesus Christ commanded His Apostles and their successors to the end of time to teach
and rule the nations. He ordered the nations to accept their teaching and obey their
authority. But his correlation of rights and duties in the Christian commonwealth not only
could not have been made permanent, but could not even have been initiated except through
the senses, which are of all things the messengers and interpreters.
For this reason the Church is so often called in Holy Writ a body, and even the body
of Christ - "Now you are the body of Christ" (I Cor. xii., 27) - and
precisely because it is a body is the Church visible: and because it is the body of Christ
is it living and energizing, because by the infusion of His power Christ guards and
sustains it, just as the vine gives nourishment and renders fruitful the branches united
From this it follows that those who arbitrarily conjure up and picture to themselves a
hidden and invisible Church are in grievous and pernicious error: as also are those who
regard the Church as a human institution which claims a certain obedience in discipline
and external duties, but which is without the perennial communication of the gifts of
divine grace, and without all that which testifies by constant and undoubted signs to the
existence of that life which is drawn from God. It is assuredly as impossible that the
Church of Jesus Christ can be the one or the other, as that man should be a body alone or
a soul alone. The connection and union of both elements is as absolutely necessary to the
true Church as the intimate union of the soul and body is to human nature. The Church is
not something dead: it is the body of Christ endowed with supernatural life. As Christ,
the Head and Exemplar, is not wholly in His visible human nature, which Photinians and
Nestorians assert, nor wholly in the invisible divine nature, as the Monophysites hold,
but is one, from and in both natures, visible and invisible; so the mystical body of
Christ is the true Church, only because its visible parts draw life and power from the
supernatural gifts and other things whence spring their very nature and essence. But since
the Church is such by divine will and constitution, such it must uniformly remain to the
end of time. If it did not, then it would not have been founded as perpetual, and the end
set before it would have been limited to some certain place and to some certain period of
time; both of which are contrary to the truth.
It is so evident from the clear and frequent testimonies of Holy Writ that the true
Church of Jesus Christ is one, that no Christian can dare to deny it. But in
judging and determining the nature of this unity many have erred in various ways.
"The Church in respect of its unity belongs to the category of things indivisible
by nature, though heretics try to divide it into many parts...We say, therefore, that the
Catholic Church is unique in its essence, in its doctrine, in its origin, and in its
excellence... Furthermore, the eminence of the Church arises from its unity, as the
principle of its constitution - a unity surpassing all else, and having nothing like unto
it or equal to it" (S. Clemens Alexandrinus, Stronmatum lib. viii., c. 17).
But the mission of Christ is to save that which had perished: that is to say,
not some nations or peoples, but the whole human race, without distinction of time or
place. The Church, therefore, is bound to communicate without stint to all men, and to
transmit through all ages, the salvation effected by Jesus Christ, and the blessings
flowing there from. Wherefore, by the will of its Founder, it is necessary that this
Church should be one in all lands and at all times.
Furthermore, the Son of God decreed that the Church should be His mystical body, with
which He should be united as the Head, after the manner of the human body which He
assumed, to which the natural head is physiologically united. As He took to Himself a
mortal body, which He gave to suffering and death in order to pay the price of man's
redemption, so also He has one mystical body in which and through which He renders men
partakers of holiness and of eternal salvation. God "hath made Him (Christ) head over
all the Church, which is His body" (Eph. i., 22-23). Scattered and separated members
cannot possibly cohere with the head so as to make one body. But St. Paul says: "All
members of the body, whereas they are many, yet are one body, so also is Christ" (I
Cor. xii., 12).
The Church of Christ, therefore, is one and the same for ever; those who leave it
depart from the will and command of Christ, the Lord - leaving the path of salvation they
enter on that of perdition.
Agreement and union of minds is the necessary foundation of this perfect concord
amongst men, from which concurrence of wills and similarity of action are the natural
results. Wherefore, in His divine wisdom, He ordained in His Church Unity of Faith;
a virtue which is the first of those bonds which unite man to God, and whence we receive
the name of the faithful - "one Lord, one faith, one baptism" (Eph. iv.,
5). That is, as there is one Lord and one baptism, so should all Christians, without
exception, have but one faith.
The heavenly doctrine of Christ, although for the most part committed to writing by
divine inspiration, could not unite the minds of men if left to the human intellect alone.
It would, for this very reason, be subject to various and contradictory interpretations.
This is so, not only because of the nature of the doctrine itself and of the mysteries it
involves, but also because of the divergencies of the human mind and of the disturbing
element of conflicting passions. From a variety of interpretations a variety of beliefs is
necessarily begotten; hence come controversies, dissensions and wranglings such as have
arisen in the past, even in the first ages of the Church.
It was the duty of all who heard Jesus Christ, if they wished for eternal salvation,
not merely to accept His doctrine as a whole, but to assent with their entire mind to all
and every point of it, since it is unlawful to withhold faith from God even in regard to
one single point.
When about to ascend into heaven He sends His Apostles in virtue of the same power by
which He had been sent from the Father; and he charges them to spread abroad and propagate
His teaching. "All power is given to Me in Heaven and in earth. Going therefore teach
all nations....teaching them to observe all things whatsoever I have commanded you"
(Matt. xxviii., 18-19- 20). So that those obeying the Apostles might be saved, and those
disobeying should perish. "He that believeth and is baptized shall be saved, but he
that believed not shall be condemned" (Mark xvi., 16). But since it is obviously most
in harmony with God's providence that no one should have confided to him a great and
important mission unless he were furnished with the means of properly carrying it out, for
this reason Christ promised that He would send the Spirit of Truth to His Disciples to
remain with them for ever. "But if I go I will send Him (the Paraclete) to you....But
when He, the Spirit of Truth is come, He will teach you all truth" John xvi., 7 13).
Wherefore the Apostles are ambassadors of Christ as He is the ambassador of the Father.
"As the Father sent Me so also I send you" John xx., 21). Hence as the Apostles
and Disciples were bound to obey Christ, so also those whom the Apostles taught were, by
God's command, bound to obey them. And, therefore, it was no more allowable to repudiate
one iota of the Apostles' teaching than it was to reject any point of the doctrine of
But, as we have already said, the Apostolic mission was not destined to die with the
Apostles themselves, or to come to an end in the course of time, since it was intended for
the people at large and instituted for the salvation of the human race. For Christ
commanded His Apostles to preach the "Gospel to every creature, to carry His name to
nations and kings, and to be witnesses to him to the ends of the earth." He further
promised to assist them in the fulfilment of their high mission, and that, not for a few
years or centuries only, but for all time - "even to the consummation of the
world." But how could all this be realized in the Apostles alone, placed as they were
under the universal law of dissolution by death? It was consequently provided by God that
the Magisterium instituted by Jesus Christ should not end with the life of the
Apostles, but that it should be perpetuated. We see it in truth propagated, and, 'as it
were, delivered from hand to hand. For the Apostles consecrated bishops, and each one
appointed those who were to succeed them immediately "in the ministry of the
Nay more: they likewise required their successors to choose fitting men, to endow them
with like authority, and to confide to them the office and mission of teaching.
"Thou, therefore, my son, be strong in the grace which is in Christ Jesus: and the
things which thou hast heard of me by many witnesses, the same command to faithful men,
who shall be fit to teach others also" (2 Tim. ii., 1-2). Wherefore, as Christ was
sent by God and the Apostles by Christ, so the Bishops and those who succeeded them were
sent by the Apostles.
9. The Church, founded on these principles and mindful of her office, has done nothing
with greater zeal and endeavour than she has displayed in guarding the integrity of the
faith. Hence she regarded as rebels and expelled from the ranks of her children all who
held beliefs on any point of doctrine different from her own. The Arians, the Montanists,
the Novatians, the Quartodecimans, the Eutychians, did not certainly reject all Catholic
doctrine: they abandoned only a certain portion of it. Still who does not know that they
were declared heretics and banished from the bosom of the Church? In like manner were
condemned all authors of heretical tenets who followed them in subsequent ages.
Wherefore, as appears from what has been said, Christ instituted in the Church a living,
authoritative and permanent Magisterium, which by His own power He strengthened, by
the Spirit of truth He taught, and by miracles confirmed. He willed and ordered, under the
gravest penalties, that its teachings should be received as if they were His own. As
often, therefore, as it is declared on the authority of this teaching that this or that is
contained in the deposit of divine revelation, it must be believed by every one as true.
If it could in any way be false, an evident contradiction follows; for then God Himself
would be the author of error in man.
For this reason the Fathers of the Vatican Council laid down nothing new, but followed
divine revelation and the acknowledged and invariable teaching of the Church as to the
very nature of faith, when they decreed as follows: "All those things are to be
believed by divine and Catholic faith which are contained in the written or unwritten word
of God, and which are pro posed by the Church as divinely revealed, either by a solemn
definition or in the exercise of its ordinary and universal Magisterium" (Sess. iii.,
cap. 3). Hence, as it is clear that God absolutely willed that there should be unity in
His Church, and as it is evident what kind of unity He willed, and by means of what
principle He ordained that this unity should be maintained, we may address the following
words of St. Augustine to all who have not deliberately closed their minds to the truth:
"When we see the great help of God, such manifest progress and such abundant fruit,
shall we hesitate to take refuge in the bosom of that Church, which, as is evident to all,
possesses the supreme authority of the Apostolic See through the Episcopal succession? In
vain do heretics rage round it; they are condemned partly by the judgment of the people
themselves, partly by the weight of councils, partly by the splendid evidence of miracles.
To refuse to the Church the primacy is most impious and above measure arrogant. And if all
learning, no matter how easy and common it may be, in order to be fully understood
requires a teacher and master, what can be greater evidence of pride and rashness than to
be unwilling to learn about the books of the divine mysteries from the proper interpreter,
and to wish to condemn them unknown?" (De Unitate Credendi, cap. xvii., n.
It is then undoubtedly the office of the church to guard Christian doctrine and to
propagate it in its integrity and purity. But this is not all: the object for which the
Church has been instituted is not wholly attained by the performance of this duty. For,
since Jesus Christ delivered Himself up for the salvation of the human race, and to this
end directed all His teaching and commands, so He ordered the Church to strive, by the
truth of its doctrine, to sanctify and to save mankind. But faith alone cannot compass so
great, excellent, and important an end. There must needs be also the fitting and devout
worship of God, which is to be found chiefly in the divine Sacrifice and in the
dispensation of the Sacraments, as well as salutary laws and discipline. All these must be
found in the Church, since it continues the mission of the Saviour for ever. The Church
alone offers to the human race that religion - that state of absolute perfection - which
He wished, as it were, to be incorporated in it. And it alone supplies those means
of salvation which accord with the ordinary counsels of Providence.
10. But as this heavenly doctrine was never left to the arbitrary judgment of private
individuals, but, in the beginning delivered by Jesus Christ, was afterwards committed by
Him exclusively to the Magisterium already named, so the power of performing and
administering the divine mysteries, together with the authority of ruling and governing,
was not bestowed by God on all Christians indiscriminately, but on certain chosen persons.
For to the Apostles and their legitimate successors alone these words have reference:
"Going into the whole world preach the Gospel." "Baptizing them."
"Do this in commemoration of Me." "Whose sins you shall forgive they are
forgiven them." And in like manner He ordered the Apostles only and those who should
lawfully succeed them to feed - that is to govern with authority - all Christian
Wherefore Jesus Christ bade all men, present and future, follow Him as their leader and
Saviour; and this, not merely as individuals, but as forming a society, organized and
united in mind. In this way a duly constituted society should exist, formed out of the
divided multitude of peoples, one in faith, one in end, one in the participation of the
means adapted to the attainment of the end, and one as subject to one and the same
authority. To this end He established in the Church all principles which necessarily tend
to make organized human societies, and through which they attain the perfection proper to
each. That is, in it (the Church), all who wished to be the sons of God by adoption might
attain to the perfection demanded by their high calling, and might obtain salvation. The
Church, therefore, as we have said, is man's guide to whatever pertains to Heaven. This is
the office appointed unto it by God: that it may watch over and may order all that
concerns religion, and may, without let or hindrance, exercise, according to its judgment,
its charge over Christianity.
God indeed even made the Church a society far more perfect than any other. For the end
for which the Church exists is as much higher than the end of other societies as divine
grace is above nature, as immortal blessings are above the transitory things on the earth.
Therefore the Church is a society divine in its origin, supernatural in its
end and in means proximately adapted to the attainment of that end; but it is a human
community inasmuch as it is composed of men.
Indeed no true and perfect human society can be conceived which is not governed by some
supreme authority. Christ therefore must have given to His Church a supreme authority to
which all Christians must render obedience. For this reason, as the unity of the faith is
of necessity required for the unity of the church, inasmuch as it is the body of the
faithful, so also for this same unity, inasmuch as the Church is a divinely
constituted society, unity of government, which effects and involves unity of communion,
is necessary jure divino [by divine law].
[For the nature of this supreme authority, see the continuation of Satis cognitum
in the section on the papacy. Satis cognitum, in its unabridged form, contains many
more texts from the Fathers of the Church in support of each of its points.]
Excerpted and abridged from Leo XIII's encylical letter on the unity of the Church, Satis
cognitum, 29 June, 1896.
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