QUESTION 2
The Existence of God
As is clear from what was said above, the main purpose of sacred doctrine is to propound our
cognition of God—not just our cognition of God as He is in Himself, but also our cognition of Him
insofar as He is the origin of things and their end, and especially insofar as He is the origin and end of the
rational creature. Therefore, since our intention is to lay out this doctrine, we will deal first with God
(Part 1); second, with the rational creature’s movement toward God (Part 2); and third, with Christ, who,
insofar as He is a man, is our way of going to God (Part 3).
Our treatment of God will be divided into three parts. We will deal, first, with those things that
pertain to the divine essence (questions 2-26); second, with those things that pertain to the distinction
among the divine Persons (questions 27-43); and, third, with those things that pertain to the procession of
creatures from God (questions 44-119).
As far as the divine essence is concerned, we must first inquire into whether there is a God
(question 2); second, we must inquire into what His mode of being is or, rather, what it is not (questions
3-13); and, third, we must inquire into those things that pertain to His operation, viz., His knowledge and
His will and power (questions 14-26).
As for the first point, there are three questions: (1) Is it known per se that there is a God? (2) Is it
demonstrable that there is a God? (3) Is there a God?
Article 1
Is it known per se that there is a God?
It seems to be known per se that there is a God:
Objection 1: The things said to be known to us per se are such that the cognition of them is in us
by nature, as is clear in the case of first principles. But, as Damascene puts it at the beginning of his
book, “The cognition of God’s existence is naturally instilled in everyone.” Therefore, it is known per se
that there is a God.
Objection 2: The things said to be known per se are such that, once their terms are understood,
they are immediately known; in Posterior Analytics 1 the Philosopher ascribes this status to first
principles—for instance, once someone knows what a whole is and what a part is, he immediately knows
that every whole is greater than a part of itself. But once someone understands what the name ‘God’
signifies, he immediately has it that there is a God. For what is signified by this name is that than which
a greater cannot be signified; but what exists in reality and in the understanding is greater than what
exists only in the understanding; since, then, God immediately exists in the understanding when the name
‘God’ is understood, it follows that He also exists in reality. Therefore, it is known per se that there is a
God.
Objection 3: It is known per se that truth exists, since anyone who denies that truth exists is
admitting that truth does exist—for if truth does not exist, then it is true that truth does not exist, and if
something is true, then it must be the case that truth exists. But according to John 14:6 (“I am the way,
the truth, and the life”), God is truth itself. Therefore, it is known per se that there is a God.
But contrary to this: As is clear from what the Philosopher says in Metaphysics 4 and Posterior
Analytics 1 about the first principles of demonstration, no one can think the opposite of something that is
known per se. But according to Psalm 52:1 (“The fool said in his heart: There is no God”), someone can
think the opposite of the proposition that there is a God. Therefore, it is not known per se that there is a
Part 1, Question 2 13
God.
I respond: There are two ways in which something can be known per se: in one way, in its own
right (secundum se) but not to us (quoad nos); in the second way, both in its own right and to us.
For a proposition is known per se because the predicate is included in the definition (ratio) of the
subject. For instance, Man is an animal is known per se because animal is part of the definition of man.
So if the real definitions (quid est) of the predicate and of the subject are known to everyone, then the
relevant proposition will be known per se to everyone. This is clearly the case with the first principles of
demonstration, whose terms are certain common notions that no one is unacquainted with, e.g., being and
non-being, whole and part, etc.
However, if there are some who are ignorant of the real definitions of the predicate and of the
subject, the proposition in question will, to be sure, be known per se as far as it itself is concerned, but it
will not be known per se to those who are unacquainted with the predicate and the subject of the
proposition. And so, as Boethius says in De Hebdomadibus, some mental conceptions are such that it is
only to the wise that they are common and known per se—as, for instance, that incorporeal beings do not
exist in a place.
I claim that the proposition ‘There is a God’ is known per se as far as it itself is concerned, since
the predicate is the same as the subject. For as will become clear below (q. 3, a. 4), God is His own esse.
But because we do not know the real definition of God, this proposition is not known per se to us.
Instead, it has to be demonstrated by means of things that are more known to us and less known by their
nature, viz., God’s effects.
Reply to objection 1: The cognition that there is a God is naturally instilled in us in a certain
general and indistinct way—viz., insofar as God is man’s beatitude. For man by nature desires beatitude,
and what man desires by nature is such that it is known to him by nature.
But this is not to know, without qualification, that there is a God—just as knowing that someone is
approaching is not the same as knowing that Peter is approaching, even if it is Peter who is approaching.
For there are many who think that man’s complete good, i.e., his beatitude, is wealth, whereas others
think it is pleasure, and still others something else.
Reply to objection 2: It might be that someone who hears the name ‘God’ does not take it that
what is being signified is that than which a greater cannot be thought. For some have believed that God
is a corporeal being.
However, even granted that someone thinks that what is signified by the name ‘God’ is what was
just said—viz., that than which a greater cannot be thought—it still does not thereby follow that he thinks
that what is signified by the name exists in reality rather than just in the intellect’s apprehension. Nor
can one argue that it does exist in reality, unless it is granted that there exists in reality something such
that a greater cannot be thought. But this is not granted by those who claim that there is no God.
Reply to objection 3: It is known per se that truth in general exists, but it is not known to us per se
that there is a First Truth.
Article 2
Can it be demonstrated that there is a God?
It seems that it cannot be demonstrated that there is a God:
Objection 1: It is an article of the faith that there is a God. But those things that belong to the
faith are not demonstrable; for a demonstration makes it the case that one knows (scire), but, as is clear
Part 1, Question 2 14
from the Apostle in Hebrews 11:1, faith is about things that are not apparent. Therefore, it cannot be
demonstrated that there is a God.
Objection 2: The middle term of a demonstration is a real definition (quid est). But as Damascene
says, in the case of God we cannot know His real definition; rather, we can know only what He is not.
Therefore, we cannot demonstrate that there is a God.
Objection 3: If one were to demonstrate that there is a God, this could only be by means of His
effects. But God’s effects are not proportionate to Him; for He is infinite and His effects are finite, and
there is no ratio of the finite to the infinite. Given, then, that a cause cannot be demonstrated by means of
an effect that is not proportionate to it, it seems that it cannot be demonstrated that there is a God.
But contrary to this: In Romans 1:20 the Apostle says, “The invisible things of God . . . are
clearly seen, being understood through the things that are made.” But this would not be so if were it not
the case that it can be demonstrated that there is a God. For the first thing that has to be understood of
something is whether it exists.
I respond: There are two kinds of demonstration. One kind is through a cause and is called a
demonstration propter quid—and this sort of demonstration is through things that are prior, absolutely
speaking. The second kind is through an effect and is called a demonstration quia—and this sort of
demonstration is through things that are prior with respect to us. For since an effect is more apparent to
us than its cause, we proceed through the effect to a cognition of the cause.
Now from any effect it can be demonstrated that a cause proper to it exists—as long as its effects
are more known to us. For since effects depend on a cause, it follows that once an effect is posited, it
must be that its cause exists prior to it. Hence, insofar as it is not known to us per se there is a God, this
is demonstrable though effects that are known to us.
Reply to objection 1: ‘There is a God’ and other things of this sort that, according to Romans
1:19, are known through natural reason are not articles of the faith but are instead preambles to the
articles. For faith presupposes natural cognition in the way that grace presupposes nature and in the way
that perfection presupposes the perfectible. But nothing prevents what is demonstrable and knowable in
its own right from being accepted as an object of faith by someone who does not grasp the
demonstration.
Reply to objection 2: When a cause is being demonstrated through an effect, the effect has to be
used in place of a real definition of the cause in order to prove that the cause exists. This is especially so
in the case of God. For in order to prove that something exists, one must take a nominal definition (quid
significat nomen)—and not a real definition (quid est)—as the middle term, since the question “What is
it?” is posterior to the question “Is there such a thing?”. But as will be shown below (q. 13, a. 1), the
names of God are imposed on the basis of His effects. Hence, when we are demonstrating that there is a
God on the basis of His effects, we can use a nominal definition of the name ‘God’ as the middle term.
Reply to objection 3: The perfect cognition of a cause cannot be had through effects that are not
proportionate to the cause. However, as was said above, from any effect it can be clearly demonstrated
to us that the cause exists. And so from God’s effects it can be demonstrated that there is a God, even
though we cannot, through those causes, know Him perfectly with respect to His essence.
Article 3
Is there a God?
It seems that there is no God:
Part 1, Question 2 15
Objection 1: If one of a pair of contraries were infinite, it would totally destroy the other contrary.
But by the name ‘God’ one means a certain infinite good. Therefore, if there were a God, there would be
no evil. But there is evil in the world. Therefore, there is no God.
Objection 2: What can be accomplished with fewer principles is not done through more
principles. But it seems that everything that happens in the world could have been accomplished through
other principles, even if there were no God; for things that are natural are traced back to nature as a
principle, whereas things that are purposeful are traced back to human reason or will as a principle.
Therefore, there is no need to claim that there is a God.
But contrary to this: Exodus 1:14 says under the personage of God, “I am Who am.”
I respond: There are five ways to prove that there is a God.
The first and clearest way is that taken from movement or change (ex parte motus):
It is certain, and obvious to the senses, that in this world some things are moved.
But everything that is moved is moved by another. For nothing is moved except insofar as it is in
potentiality with respect to that actuality toward which it is moved, whereas something effects movement
insofar as it is in actuality in a relevant respect. After all, to effect movement (movere) is just to lead
something from potentiality into actuality. But a thing cannot be led from potentiality into actuality
except through some being that is in actuality in a relevant respect; for example, something that is hot in
actuality—say, a fire—makes a piece of wood, which is hot in potentiality, to be hot in actuality, and it
thereby moves and alters the piece of wood. But it is impossible for something to be simultaneously in
potentiality and in actuality with respect to same thing; rather, it can be in potentiality and in actuality
only with respect to different things. For what is hot in actuality cannot simultaneously be hot in
potentiality; rather, it is cold in potentiality. Therefore, it is impossible that something should be both
mover and moved in the same way and with respect to the same thing, or, in other words, that something
should move itself. Therefore, everything that is moved must be moved by another.
If, then, that by which something is moved is itself moved, then it, too, must be moved by another,
and that other by still another. But this does not go on to infinity. For if it did, then there would not be
any first mover and, as a result, none of the others would effect movement, either. For secondary movers
effect movement only because they are being moved by a first mover, just as a stick does not effect
movement except because it is being moved by a hand. Therefore, one has to arrive at some first mover
that is not being moved by anything. And this is what everyone takes to be a God.
The second way is based on the notion of an efficient cause:
We find that among sensible things there is an ordering of efficient causes, and yet we do not
find—nor is it possible to find—anything that is an efficient cause of its own self. For if something were
an efficient cause of itself, then it would be prior to itself—which is impossible.
But it is impossible to go on to infinity among efficient causes. For in every case of ordered
efficient causes, the first is a cause of the intermediate and the intermediate is a cause of the last—and
this regardless of whether the intermediate is constituted by many causes or by just one. But when a
cause is removed, its effect is removed. Therefore, if there were no first among the efficient causes, then
neither would there be a last or an intermediate. But if the efficient causes went on to infinity, there
would not be a first efficient cause, and so there would not be a last effect or any intermediate efficient
causes, either—which is obviously false. Therefore, one must posit some first efficient cause—which
everyone calls a God.
The third way is taken from the possible and the necessary, and it goes like this:
Certain of the things we find in the world are able to exist and able not to exist (quaedam quae sunt
possibilia esse et non esse); for some things are found to be generated and corrupted and, as a result, they
are able to exist and able not to exist.
But it is impossible that everything that exists should be like this; for that which is able not to exist
Part 1, Question 2 16
is such that at some time it does not exist. Therefore, if everything is such that it is able not to exist, then
at some time nothing existed in the world. But if this were true, then nothing would exist even now. For
what does not exist begins to exist only through something that does exist; therefore, if there were no
beings, then it was impossible that anything should have begun to exist, and so nothing would exist
now—which is obviously false. Therefore, not all beings are able to exist [and able not to exist]; rather,
it must be that there is something necessary in the world.
Now every necessary being either has a cause of its necessity from outside itself or it does not. But
it is impossible to go on to infinity among necessary beings that have a cause of their necessity—in the
same way, as was proved above, that it is impossible to go on to infinity among efficient causes.
Therefore, one must posit something that is necessary per se, which does not have a cause of its necessity
from outside itself but is instead a cause of necessity for the other [necessary] things. But this everyone
calls a God.
The fourth way is taken from the gradations that are found in the world:
In the world some things are found to be more and less good, more and less true, more and less
noble, etc. But more and less are predicated of diverse things insofar as they approach in diverse ways
that which is maximal in a given respect. For instance, the hotter something is, the closer it approaches
that which is maximally hot. Therefore, there is something that is maximally true, maximally good, and
maximally noble, and, as a result, is a maximal being; for according to the Philosopher in Metaphysics 2,
things that are maximally true are maximally beings.
But, as is claimed in the same book, that which is maximal in a given genus is a cause of all the
things that belong to that genus; for instance, fire, which is maximally hot, is a cause of all hot things.
Therefore, there is something that is a cause for all beings of their esse, their goodness, and each of their
perfections—and this we call a God.
The fifth way is taken from the governance of things:
We see that some things lacking cognition, viz., natural bodies, act for the sake of an end. This is
apparent from the fact that they always or very frequently act in the same way in order to bring about
what is best, and from this it is clear that it is not by chance (non a casu), but as the result of a tendency
(ex intentione), that they attain the end.
But things lacking cognition tend toward an end only if they are directed by something that has
cognition and intellective understanding (non tendunt in finem nisi directa ab aliquo cognoscente et
intelligente), in the way that an arrow is directed by an archer. Therefore, there is something with
intellective understanding by which all natural things are ordered toward an end—and this we call a God.
Reply to objection 1: As Augustine says in the Enchiridion, “Since God is maximally good, He
would not allow any evil to exist in His works if He were not powerful enough and good enough to draw
good even from evil.” Therefore, it is part of God’s infinite goodness that He should permit evils and
elicit goods from them.
Reply to objection 2: Since it is by the direction of a higher agent that nature acts for the sake of a
determinate end, those things that are done by nature must also be traced back to God as a first cause.
Similarly, even things that are done by design must be traced back to a higher cause and not to human
reason and will. For human reason and will are changeable and subject to failure, but, as was shown
above, all things that can change and fail must be traced back to a first principle that is unmoved and
necessary per se.
The Existence of God
As is clear from what was said above, the main purpose of sacred doctrine is to propound our
cognition of God—not just our cognition of God as He is in Himself, but also our cognition of Him
insofar as He is the origin of things and their end, and especially insofar as He is the origin and end of the
rational creature. Therefore, since our intention is to lay out this doctrine, we will deal first with God
(Part 1); second, with the rational creature’s movement toward God (Part 2); and third, with Christ, who,
insofar as He is a man, is our way of going to God (Part 3).
Our treatment of God will be divided into three parts. We will deal, first, with those things that
pertain to the divine essence (questions 2-26); second, with those things that pertain to the distinction
among the divine Persons (questions 27-43); and, third, with those things that pertain to the procession of
creatures from God (questions 44-119).
As far as the divine essence is concerned, we must first inquire into whether there is a God
(question 2); second, we must inquire into what His mode of being is or, rather, what it is not (questions
3-13); and, third, we must inquire into those things that pertain to His operation, viz., His knowledge and
His will and power (questions 14-26).
As for the first point, there are three questions: (1) Is it known per se that there is a God? (2) Is it
demonstrable that there is a God? (3) Is there a God?
Article 1
Is it known per se that there is a God?
It seems to be known per se that there is a God:
Objection 1: The things said to be known to us per se are such that the cognition of them is in us
by nature, as is clear in the case of first principles. But, as Damascene puts it at the beginning of his
book, “The cognition of God’s existence is naturally instilled in everyone.” Therefore, it is known per se
that there is a God.
Objection 2: The things said to be known per se are such that, once their terms are understood,
they are immediately known; in Posterior Analytics 1 the Philosopher ascribes this status to first
principles—for instance, once someone knows what a whole is and what a part is, he immediately knows
that every whole is greater than a part of itself. But once someone understands what the name ‘God’
signifies, he immediately has it that there is a God. For what is signified by this name is that than which
a greater cannot be signified; but what exists in reality and in the understanding is greater than what
exists only in the understanding; since, then, God immediately exists in the understanding when the name
‘God’ is understood, it follows that He also exists in reality. Therefore, it is known per se that there is a
God.
Objection 3: It is known per se that truth exists, since anyone who denies that truth exists is
admitting that truth does exist—for if truth does not exist, then it is true that truth does not exist, and if
something is true, then it must be the case that truth exists. But according to John 14:6 (“I am the way,
the truth, and the life”), God is truth itself. Therefore, it is known per se that there is a God.
But contrary to this: As is clear from what the Philosopher says in Metaphysics 4 and Posterior
Analytics 1 about the first principles of demonstration, no one can think the opposite of something that is
known per se. But according to Psalm 52:1 (“The fool said in his heart: There is no God”), someone can
think the opposite of the proposition that there is a God. Therefore, it is not known per se that there is a
Part 1, Question 2 13
God.
I respond: There are two ways in which something can be known per se: in one way, in its own
right (secundum se) but not to us (quoad nos); in the second way, both in its own right and to us.
For a proposition is known per se because the predicate is included in the definition (ratio) of the
subject. For instance, Man is an animal is known per se because animal is part of the definition of man.
So if the real definitions (quid est) of the predicate and of the subject are known to everyone, then the
relevant proposition will be known per se to everyone. This is clearly the case with the first principles of
demonstration, whose terms are certain common notions that no one is unacquainted with, e.g., being and
non-being, whole and part, etc.
However, if there are some who are ignorant of the real definitions of the predicate and of the
subject, the proposition in question will, to be sure, be known per se as far as it itself is concerned, but it
will not be known per se to those who are unacquainted with the predicate and the subject of the
proposition. And so, as Boethius says in De Hebdomadibus, some mental conceptions are such that it is
only to the wise that they are common and known per se—as, for instance, that incorporeal beings do not
exist in a place.
I claim that the proposition ‘There is a God’ is known per se as far as it itself is concerned, since
the predicate is the same as the subject. For as will become clear below (q. 3, a. 4), God is His own esse.
But because we do not know the real definition of God, this proposition is not known per se to us.
Instead, it has to be demonstrated by means of things that are more known to us and less known by their
nature, viz., God’s effects.
Reply to objection 1: The cognition that there is a God is naturally instilled in us in a certain
general and indistinct way—viz., insofar as God is man’s beatitude. For man by nature desires beatitude,
and what man desires by nature is such that it is known to him by nature.
But this is not to know, without qualification, that there is a God—just as knowing that someone is
approaching is not the same as knowing that Peter is approaching, even if it is Peter who is approaching.
For there are many who think that man’s complete good, i.e., his beatitude, is wealth, whereas others
think it is pleasure, and still others something else.
Reply to objection 2: It might be that someone who hears the name ‘God’ does not take it that
what is being signified is that than which a greater cannot be thought. For some have believed that God
is a corporeal being.
However, even granted that someone thinks that what is signified by the name ‘God’ is what was
just said—viz., that than which a greater cannot be thought—it still does not thereby follow that he thinks
that what is signified by the name exists in reality rather than just in the intellect’s apprehension. Nor
can one argue that it does exist in reality, unless it is granted that there exists in reality something such
that a greater cannot be thought. But this is not granted by those who claim that there is no God.
Reply to objection 3: It is known per se that truth in general exists, but it is not known to us per se
that there is a First Truth.
Article 2
Can it be demonstrated that there is a God?
It seems that it cannot be demonstrated that there is a God:
Objection 1: It is an article of the faith that there is a God. But those things that belong to the
faith are not demonstrable; for a demonstration makes it the case that one knows (scire), but, as is clear
Part 1, Question 2 14
from the Apostle in Hebrews 11:1, faith is about things that are not apparent. Therefore, it cannot be
demonstrated that there is a God.
Objection 2: The middle term of a demonstration is a real definition (quid est). But as Damascene
says, in the case of God we cannot know His real definition; rather, we can know only what He is not.
Therefore, we cannot demonstrate that there is a God.
Objection 3: If one were to demonstrate that there is a God, this could only be by means of His
effects. But God’s effects are not proportionate to Him; for He is infinite and His effects are finite, and
there is no ratio of the finite to the infinite. Given, then, that a cause cannot be demonstrated by means of
an effect that is not proportionate to it, it seems that it cannot be demonstrated that there is a God.
But contrary to this: In Romans 1:20 the Apostle says, “The invisible things of God . . . are
clearly seen, being understood through the things that are made.” But this would not be so if were it not
the case that it can be demonstrated that there is a God. For the first thing that has to be understood of
something is whether it exists.
I respond: There are two kinds of demonstration. One kind is through a cause and is called a
demonstration propter quid—and this sort of demonstration is through things that are prior, absolutely
speaking. The second kind is through an effect and is called a demonstration quia—and this sort of
demonstration is through things that are prior with respect to us. For since an effect is more apparent to
us than its cause, we proceed through the effect to a cognition of the cause.
Now from any effect it can be demonstrated that a cause proper to it exists—as long as its effects
are more known to us. For since effects depend on a cause, it follows that once an effect is posited, it
must be that its cause exists prior to it. Hence, insofar as it is not known to us per se there is a God, this
is demonstrable though effects that are known to us.
Reply to objection 1: ‘There is a God’ and other things of this sort that, according to Romans
1:19, are known through natural reason are not articles of the faith but are instead preambles to the
articles. For faith presupposes natural cognition in the way that grace presupposes nature and in the way
that perfection presupposes the perfectible. But nothing prevents what is demonstrable and knowable in
its own right from being accepted as an object of faith by someone who does not grasp the
demonstration.
Reply to objection 2: When a cause is being demonstrated through an effect, the effect has to be
used in place of a real definition of the cause in order to prove that the cause exists. This is especially so
in the case of God. For in order to prove that something exists, one must take a nominal definition (quid
significat nomen)—and not a real definition (quid est)—as the middle term, since the question “What is
it?” is posterior to the question “Is there such a thing?”. But as will be shown below (q. 13, a. 1), the
names of God are imposed on the basis of His effects. Hence, when we are demonstrating that there is a
God on the basis of His effects, we can use a nominal definition of the name ‘God’ as the middle term.
Reply to objection 3: The perfect cognition of a cause cannot be had through effects that are not
proportionate to the cause. However, as was said above, from any effect it can be clearly demonstrated
to us that the cause exists. And so from God’s effects it can be demonstrated that there is a God, even
though we cannot, through those causes, know Him perfectly with respect to His essence.
Article 3
Is there a God?
It seems that there is no God:
Part 1, Question 2 15
Objection 1: If one of a pair of contraries were infinite, it would totally destroy the other contrary.
But by the name ‘God’ one means a certain infinite good. Therefore, if there were a God, there would be
no evil. But there is evil in the world. Therefore, there is no God.
Objection 2: What can be accomplished with fewer principles is not done through more
principles. But it seems that everything that happens in the world could have been accomplished through
other principles, even if there were no God; for things that are natural are traced back to nature as a
principle, whereas things that are purposeful are traced back to human reason or will as a principle.
Therefore, there is no need to claim that there is a God.
But contrary to this: Exodus 1:14 says under the personage of God, “I am Who am.”
I respond: There are five ways to prove that there is a God.
The first and clearest way is that taken from movement or change (ex parte motus):
It is certain, and obvious to the senses, that in this world some things are moved.
But everything that is moved is moved by another. For nothing is moved except insofar as it is in
potentiality with respect to that actuality toward which it is moved, whereas something effects movement
insofar as it is in actuality in a relevant respect. After all, to effect movement (movere) is just to lead
something from potentiality into actuality. But a thing cannot be led from potentiality into actuality
except through some being that is in actuality in a relevant respect; for example, something that is hot in
actuality—say, a fire—makes a piece of wood, which is hot in potentiality, to be hot in actuality, and it
thereby moves and alters the piece of wood. But it is impossible for something to be simultaneously in
potentiality and in actuality with respect to same thing; rather, it can be in potentiality and in actuality
only with respect to different things. For what is hot in actuality cannot simultaneously be hot in
potentiality; rather, it is cold in potentiality. Therefore, it is impossible that something should be both
mover and moved in the same way and with respect to the same thing, or, in other words, that something
should move itself. Therefore, everything that is moved must be moved by another.
If, then, that by which something is moved is itself moved, then it, too, must be moved by another,
and that other by still another. But this does not go on to infinity. For if it did, then there would not be
any first mover and, as a result, none of the others would effect movement, either. For secondary movers
effect movement only because they are being moved by a first mover, just as a stick does not effect
movement except because it is being moved by a hand. Therefore, one has to arrive at some first mover
that is not being moved by anything. And this is what everyone takes to be a God.
The second way is based on the notion of an efficient cause:
We find that among sensible things there is an ordering of efficient causes, and yet we do not
find—nor is it possible to find—anything that is an efficient cause of its own self. For if something were
an efficient cause of itself, then it would be prior to itself—which is impossible.
But it is impossible to go on to infinity among efficient causes. For in every case of ordered
efficient causes, the first is a cause of the intermediate and the intermediate is a cause of the last—and
this regardless of whether the intermediate is constituted by many causes or by just one. But when a
cause is removed, its effect is removed. Therefore, if there were no first among the efficient causes, then
neither would there be a last or an intermediate. But if the efficient causes went on to infinity, there
would not be a first efficient cause, and so there would not be a last effect or any intermediate efficient
causes, either—which is obviously false. Therefore, one must posit some first efficient cause—which
everyone calls a God.
The third way is taken from the possible and the necessary, and it goes like this:
Certain of the things we find in the world are able to exist and able not to exist (quaedam quae sunt
possibilia esse et non esse); for some things are found to be generated and corrupted and, as a result, they
are able to exist and able not to exist.
But it is impossible that everything that exists should be like this; for that which is able not to exist
Part 1, Question 2 16
is such that at some time it does not exist. Therefore, if everything is such that it is able not to exist, then
at some time nothing existed in the world. But if this were true, then nothing would exist even now. For
what does not exist begins to exist only through something that does exist; therefore, if there were no
beings, then it was impossible that anything should have begun to exist, and so nothing would exist
now—which is obviously false. Therefore, not all beings are able to exist [and able not to exist]; rather,
it must be that there is something necessary in the world.
Now every necessary being either has a cause of its necessity from outside itself or it does not. But
it is impossible to go on to infinity among necessary beings that have a cause of their necessity—in the
same way, as was proved above, that it is impossible to go on to infinity among efficient causes.
Therefore, one must posit something that is necessary per se, which does not have a cause of its necessity
from outside itself but is instead a cause of necessity for the other [necessary] things. But this everyone
calls a God.
The fourth way is taken from the gradations that are found in the world:
In the world some things are found to be more and less good, more and less true, more and less
noble, etc. But more and less are predicated of diverse things insofar as they approach in diverse ways
that which is maximal in a given respect. For instance, the hotter something is, the closer it approaches
that which is maximally hot. Therefore, there is something that is maximally true, maximally good, and
maximally noble, and, as a result, is a maximal being; for according to the Philosopher in Metaphysics 2,
things that are maximally true are maximally beings.
But, as is claimed in the same book, that which is maximal in a given genus is a cause of all the
things that belong to that genus; for instance, fire, which is maximally hot, is a cause of all hot things.
Therefore, there is something that is a cause for all beings of their esse, their goodness, and each of their
perfections—and this we call a God.
The fifth way is taken from the governance of things:
We see that some things lacking cognition, viz., natural bodies, act for the sake of an end. This is
apparent from the fact that they always or very frequently act in the same way in order to bring about
what is best, and from this it is clear that it is not by chance (non a casu), but as the result of a tendency
(ex intentione), that they attain the end.
But things lacking cognition tend toward an end only if they are directed by something that has
cognition and intellective understanding (non tendunt in finem nisi directa ab aliquo cognoscente et
intelligente), in the way that an arrow is directed by an archer. Therefore, there is something with
intellective understanding by which all natural things are ordered toward an end—and this we call a God.
Reply to objection 1: As Augustine says in the Enchiridion, “Since God is maximally good, He
would not allow any evil to exist in His works if He were not powerful enough and good enough to draw
good even from evil.” Therefore, it is part of God’s infinite goodness that He should permit evils and
elicit goods from them.
Reply to objection 2: Since it is by the direction of a higher agent that nature acts for the sake of a
determinate end, those things that are done by nature must also be traced back to God as a first cause.
Similarly, even things that are done by design must be traced back to a higher cause and not to human
reason and will. For human reason and will are changeable and subject to failure, but, as was shown
above, all things that can change and fail must be traced back to a first principle that is unmoved and
necessary per se.