For Aquinas, the Trinity is at the heart of Christian teaching,
and our understanding of it comes solely from Scripture (and
teaching which conforms to Scripture). He thinks we can reason
to the existence of God, but not to the Trinity; if we know about
the Trinity, it's only because of what Christ has said, not because
of anything we could have figured out for ourselves. However,
Aquinas thinks we can explore what the patterns might mean that
are described in Scripture and Church teaching about the makeup
of the unknowable cause of existence, and this he does.
Here's his take on the Trinity.
Aquinas thinks that the Father, the Son and the Holy Spirit,
while referred to as 'persons,' are not in any way like separate
individuals in the category God (e.g., the Father as the 'old
man,' the Son as the 'young man,' the Holy Spirit as the 'dove').
He thinks the essential distinction that makes up the Trinity
is one of relationships (i.e., states of being connected
or ways in which two or more things are connected) that
And what these
relationships describe is God's self-knowledge and love.
of consciousness out there ought to have a great time with this
And what might that mean? Think about how you know yourself
and how you feel about yourself. First of all, there is you.
And because you are self-aware, you form a concept of yourself,
which you can come to know. This causes you to
with yourself, between the two end-points of self and
Your self-knowledge is distinct from you but is definitely
a part of you, and you could even
say it proceeds from you. In humans, self-knowledge usually evolves
in childhood when we reach the age of reason, somewhere
first or second grade (e.g., Lizzie, six years old, saying: "Mom,
why do I have to be a separate person?"). So each of us,
being self-aware, has a relationship of knowledge between ourselves
and the concept we have of ourselves.
And the two
relationship (self and self-knowledge) also have a relationship
of varying degrees of love or hate: we
hate ourselves, or are rather pleased with ourselves, or
are somewhere in the middle.
a relationship of self-knowledge
Aquinas, in line with a solid
theological tradition and particularly with St. Augustine,
thinks that the
same sort of relationship of self-knowledge and love going on
in God. God the Father represents God. Proceeding from God
is God's concept of himself, or his self-knowledge;
the self-knowledge of God is
of as God the Son. And the Holy Spirit is the
relationship of love between God's self-knowledge and God.
Here's the analogy he uses to explain it, echoing the beginning
of the Gospel of John and relating it to the
use of language (which inevitably turns up when we
speak of self-knowledge):
"Whenever anyone understands because of his very act
of understanding, something comes forth within him, which is
the concept of the known thing proceeding from his awareness
of it. It is this concept which an utterance signifies; we
call it 'the word in the heart' signified by the spoken word."
So Aquinas thinks that the Son of God (or the Word, as Christ
is called in the Gospel of John), is God as known to God; the
Son of God is God's self-knowledge or awareness.
a relationship of love
And what of the Holy Spirit? He sees the
Holy Spirit as the loving relationship between God's self-knowledge
When you love something, it makes an imprint on you:
"The object loved is present in the lover even as the
object known is present in the knower." (ST 1a.27.3)
This imprint of the love between the Father and the Son is
what Aquinas thinks of as the Holy Spirit. In the Trinity, the
and the Son are known and loved by each other, and the love that
proceeds from that relationship is the Holy Spirit.
This is the sense that Aquinas makes of what he has understood
from Scripture about the three-part nature of God:
the essential distinction that makes up the Trinity is one of
relationship, with God as the Father, God the Son as the self-knowledge
or awareness that proceeds from the Father (God as known to God),
and the Holy Spirit as the love proceeding from the relationship
Aquinas also thinks that in knowing himself, God also knows
his creatures, as he thinks us into existence as well, so we
are a part of his self-knowledge.
"In knowing himself, God knows
every creature ... Because by the one act he understands both
himself and all else, his single Word expresses not only the
Father but creatures as well." (3A, 34, 4)
So we are known,
and also loved:
"The Father loves not only the Son but himself and us in the
Holy Spirit, because the Holy Spirit comes forth as a love of
the primal goodness with which God loves himself and all his
creatures." (3A, 37, 1)
The cause of
the ultimate mystery of existence is self-aware and perfectly
happy, a graced state
with knowledge and love. Ah, truly, only a divine being
could pull that one off. But we at least get some chance to
"Moreover the Word of God is born of God by the knowledge
of Himself; and Love proceeds from God according as He loves Himself."
"In the beginning was the Word, and the Word was with
God, and the Word was God."
"St. Thomas likens the procession of the Word in God to our
act of self-awareness when the mind is both naturally and objectively
identified with itself. So it is as if in thinking of himself
that God begets God. He is pure intelligibility, and his act
of understanding issuing in his Word is identical with his very
- Ceslaus Velecky, as quoted in The Thought of Thomas Aquinas
by Brian Davies, p.196