Introduction

The following argument is an objection to divine simplicity. Admittedly, the objection is not very rigorous nor need it sway a Thomist or other classical theist. I myself am somewhat sympathetic to the idea that the ultimate or most foundational reality must be metaphysically simple. But I am nevertheless curious about how classical theists would respond to this objection to divine simplicity.

Argument

1. Objects that are similar share a common part.
2. God has no parts. [divine simplicity]
3. If (1) and (2), then God is not similar to something else.
4. God is similar to creatures in a various ways.
5. Therefore, God is and is not similar to something else. [from 1-4, contradiction]

Defense of the premises

The view stated in premise 1 is a straightforward way of making sense of similarities between objects. Why is table A similar to table B? Because they have something in common (e.g. their shape). Premise 2 is a straightforward way of articulating the doctrine of divine simplicity, according to which God has neither physical nor metaphysical parts. Premise 3 seems to be pretty clearly true. If God has no parts, then God cannot have a part in common with something else. But, given premise 1, then God cannot be similar to something else. To deny premise 4 is very costly, since there are pretty obvious ways in which God is (or would be) similar to (some) creatures. For example, God has power and (some) creatures have power. God causes things to happen and (some) creatures cause things to happen. Moreover, analogical predication of God presupposes similarity. One cannot be analogous to something without being similar to it. Thus, (much of) our language could only apply equivocally to God, if God is not similar to anything else.

Conclusion

Lastly, the conclusion follows pretty straigthforwardly from the premises. From premises 1-3 it follows that God is not similar to something else. But it follows from premise 4 that God is similar to something else. However, this is a contradiction. Thus, assuming the argument is valid, we must either allow for true contradictions or deny one of the premises. Given that this is not a true condradiction and assuming that the other premises are true, it follows that premise 2 is false. But if premise 2 is false, then the doctrine of divine simplicity is (arguably) false.