Three proofs for unity of God


Here we discuss three proofs given by Aquinas about unity of God. This is our reference:

First argument is about the fact that God is simple and this applies only to God. Therefore there is only one God. By simple he means that God is His own nature.

Second argument is about the fact that He is infinitely perfect. Therefore there is only one God. By perfect he means that He exhaust all good attributes.

Third argument is about unity of the creation and the fact that the creation cannot be cause of different God.

My objection to the fist argument: Our minds are also simple yet they are different. Mind being the essence of any being with ability to experience, decide and cause. In fact the definition of mind applies to God too.

My objection to second argument: I can imagine two conscious beings both being perfect.

My objection to third argument: It is not obvious that there is only one universe. There could be many universes which are causally independent.


Have you read the Summa from the beginning? These objections seem like misunderstandings more than anything.


I ask because Aquinas quite adequately answers your first two objections early in the Summa. As for the 3rd objection, anything that exists would be integrated within Aquinas’ definition of the universe since God is pure being subsistent in of itself, hence all that is subsists in him, even different universes.


And if you aren’t reading the Summa in order, please do. Each argument builds on the other and is necessary to understand later articles.


May I suggest you join the Thomism Discussion Group on Facebook? You’ll have more knowledgeable people there than on the CAF to answer your questions.


No, I haven’t read the whole Summa.


It would be great if you could direct me to the place that he answer the first two objections. Two universes which are causally independent could be created by two different Gods.


Thanks. I will try to join there.


The mind is not absolutely simple.

How are the two beings distinguished? They can only be distinguished if one (or both) has something the other lacks, and therefore is not pure actuality. Therefore at least one is not perfect in the sense Aquinas means it.

Third, Aquinas isn’t just thinking of our universe, but all reality. That could include infinite universes and infinite multiverses or whatever order of existing things you propose.


They could not be, because if such were the case we could at best call them “gods” with lower case g’s, for if they were different, then neither could actually be the absolute unmoved mover, first cause, necessary being, actus purus.


Mind is absolutely simple given the definition.

The only thing which separate two minds from each other is the sense of self. Other than sense of self they are exactly similar.

I mean two universes which are causally independent could be created by two different Gods. Of course there is a tension in creation if there was only one universe and two Gods.


Why gods instead of Gods? You could have two Gods which are independent and each creates His own independent universe.


No, you couldn’t have two such Gods, for neither would be what is meant by God as understood by Christianity. Both would be something else.


What reason do you have to say the mind is absolutely simple? No individual mind is equivalent to the concept of subsistent existence, being itself. They are conditioned by whose mind it is, and what time period it exists, what nature it belongs to, what knowledge they are related to, etc… Two minds are not exactly similar. Again, you seem to simply want to define things a certain way arbitrarily, and pay little heed to whether there’s any actual good basis for doing so. “A mind is absolutely simple!” Why? “Because that’s how I define it.” But a look at reality shows that the mind is conditioned by any number of factors. “It doesn’t matter I just say it’s this by definition.” That doesn’t tell us anything useful.

Creating a universe isn’t enough to be considered “God.”


It is, otherwise it could not sustain itself.

Mind is eternal. It just have access to reality now.

What is those factors? All those factors are part of his epxerience which emerges from nature and reason.

I don’t think that God can decide to not create a universe otherwise God is not good, existence is good.


Do you have a proof that my case is wrong and your case is correct?


You have to read the summa from the beginning. You also have to understand quite a bit of Aristotelian metaphysics. Excited to see your post on the group!


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