is to be found a trace not of the Trinity
but of the unity of essence.

_On the contrary,_ Augustine says (De Trin. vi, 10), that "the trace
of the Trinity appears in creatures."

_I answer that,_ Every effect in some degree represents its cause,
but diversely. For some effects represent only the causality of the
cause, but not its form; as smoke represents fire. Such a
representation is called a "trace": for a trace shows that someone
has passed by but not who it is. Other effects represent the cause as
regards the similitude of its form, as fire generated represents fire
generating; and a statue of Mercury represents Mercury; and this is
called the representation of "image." Now the processions of the
divine Persons are referred to the acts of intellect and will, as was
said above (Q. 27). For the Son proceeds as the word of the intellect;
and the Holy Ghost proceeds as love of the will. Therefore in
rational creatures, possessing intellect and will, there is found the
representation of the Trinity by way of image, inasmuch as there is
found in them the word conceived, and the love proceeding.

But in all creatures there is found the trace of the Trinity, inasmuch
as in every creature are found some things which are necessarily
reduced to the divine Persons as to their cause. For every creature
subsists in its own being, and has a form, whereby it is determined to
a species, and has relation to something else. Therefore as it is a
created substance, it represents the cause and principle; and so in
that manner it shows the Person of the Father, Who is the "principle
from no principle." According as it has a form and species, it
represents the Word as the form of the thing made by art is from the
conception of the craftsman. According as it has relation of order, it
represents the Holy Ghost, inasmuch as He is love, because the order
of the effect to something else is from the will of the Creator. And
therefore Augustine says (De Trin. vi 10) that the trace of the
Trinity is found in every creature, according "as it is one
individual," and according "as it is formed by a species," and
according as it "has a certain relation of order." And to these also
are reduced those three, "number," "weight," and "measure," mentioned
in the Book of Wisdom (9:21). For "measure" refers to the substance of
the thing limited by its principles, "number" refers to the species,
"weight" refers to the order. And to these three are reduc