Before we enter upon this subject, it will be both desirable and
useful to say a few words about the Mystery of the Blessed
Trinity. This dogma is called by the doctors of the Church "the
substance of the New Testament," that is to say, the greatest of
all mysteries, since it is the fountain and origin of them all. In
order to know and contemplate this mystery, the angels were
created in Heaven and men upon earth. In order to teach more fully
this mystery, which was but foreshadowed in the Old Testament, God
Himself came down from the angels unto men: "No man hath seen God
at any time; the only begotten Son, who is in the bosom of the
Father, He hath declared Him" (John 1.18). Whosoever then writes
or speaks of the Trinity must keep before his eyes the prudent
warning of the Angelic Doctor: "When we speak of the Trinity, we
must do so with caution and modesty, for, as St. Augustine saith,
nowhere else are more dangerous errors made, or is research more
difficult, or discovery more fruitful" (_Summ. Th._ 1a, q. 31. _De
Trin._ 1. 1, c. 3). The danger that arises is lest the Divine
Persons be confounded one with the other in faith or worship, or
lest the one Nature in them be separated: for "This is the
Catholic Faith, that we should adore one God in Trinity and
Trinity in Unity." Therefore Our predecessor Innocent XII
absolutely refused the petition of those who desired a special
festival in honor of God the Father. For, although the separate
mysteries connected with the Incarnate Word are celebrated on
certain fixed days, yet there is no special feast on which the
Word is honored according to His Divine Nature alone. And even the
Feast of Pentecost was instituted in the earliest times, not
simply to honor the Holy Ghost in Himself, but to commemorate His
coming, or His external mission. And all this has been wisely
ordained, lest from distinguishing the Persons men should be led
to distinguish the Divine Essence. Moreover, the Church, in order
to preserve in her children the purity of faith, instituted the
Feast of the Most Holy Trinity, which John XXII afterwards
extended to the Universal Church. He also permitted altars and
churches to be dedicated to the Blessed Trinity, and, with the
divine approval, sanctioned the Order for the Ransom of Captives,
which is specially devoted to the Blessed Trinity and bears Its
name. Many facts confirm this truth. The worship paid to the
saints and angels, to the Mother of God, and to Christ Himself,
finally redounds to the honor of the Blessed Trinity. In prayers
addressed to one Person, there is also mention of the others; in
the litanies after the individual Persons have been separately
invoked, a common invocation of all is added: all psalms and hymns
conclude with the doxology to the Father, Son, and Holy Ghost;
blessings, sacred rites, and sacraments are either accompanied or
concluded by the invocation of the Blessed Trinity. This was
already foreshadowed by the Apostle in those words: "For of Him,
and by Him, and in Him, are all things: to Him be glory for ever"
(Rom. 11.36), thereby signifying both the Trinity of Persons and
the Unity of Nature: for as this is one and the same in each of
the Persons, so to each is equally owing supreme glory, as to one
and the same God. St. Augustine, commenting upon this testimony,
writes: "The words of the Apostle, _of Him, and by Him, and in
Him_, are not to be taken indiscriminately; _of Him_ refers to the
Father, _by Him_ to the Son, _in Him_ to the Holy Ghost" (_De
Trin_. 1. vi, c. 10; 1. i, c. 6). The Church is accustomed most
fittingly to attribute to the Father those works of the Divinity
in which power excels, to the Son those in which wisdom excels,
and those in which love excels to the Holy Ghost. Not that all
perfections and external operations are not common to the Divine
Persons; for "the operations of the Trinity are indivisible, even
as the essence of the Trinity is indivisible" (St. Aug. _De
Trin_., 1. 1, cc. 4-5); because as the three Divine Persons "are
inseparable, so do they act inseparably" (St. Aug., _ib_). But by
a certain comparison, and a kind of affinity between the
operations and the properties of the Persons, these operations are
attributed or, as it is said, "appropriated" to One Person rather
than to the others. "Just as we make use of the traces of
similarity or likeness which we find in creatures for the
manifestation of the Divine Persons, so do we use Their essential
attributes; and this manifestation of the Persons by Their
essential attributes is called _appropriation_" (St. Th. 1a, q.
39, xxxix, a. 7). In this manner the Father, who is "the principle
of the whole God-head" (St. Aug., _De Trin_., 1. iv, c. 20), is
also the efficient cause of all things, of the Incarnation of the
Word, and the sanctification of souls; "of Him are all things":
_of Him_, referring to the Father. But the Son, the Word, the
Image of God, is also the exemplar cause, whence all creatures
borrow their form and beauty, their order and harmony. He is for
us the Way, the Truth, and the Life; the Reconciler of man with
God. "By Him are all things": _by Him_, referring to the Son. The
Holy Ghost is the ultimate cause of all things, since, as the will
and all other things finally rest in their end, so He, who is the
Divine Goodness and the Mutual Love of the Father and Son,
completes and perfects, by His strong yet gentle power, the secret
work of man's eternal salvation. "In Him are all things": _in
Him_, referring to the Holy Ghost.