The question is whether the notion of perfection, by itself, is sufficient to explain God’s existence. If so, then perhaps one does not need to follow the classical theist in affirming divine simplicity, since perfection might be enough to provide the ultimate explanation of things.
Let’s think about this.
In the framework of perfect being theology, the concept of perfection involves identifying great-making properties—those attributes that a perfect being must possess to the maximal degree, such as omnipotence, omniscience, and necessary existence. However, there are problems with this approach. For one thing, intuitions about what constitutes a great-making property can vary. For example, is simplicity a perfection? I would argue yes, as does Anselm, who posits that God must be simple to avoid any division or parthood that could imply dependency.1 After all, at least when positioned within a constituent ontology, a God composed of different properties would depend on those (metaphysical) parts, since the whole is metaphysically downstream of those parts, making God less fundamental than the parts themselves, which is problematic for anyone who wants to maintain that God depends upon nothing—either from without or within. In other words, for God to truly be God.
Yet, others may be uncertain whether simplicity is truly a perfection. So, instead, they might argue that independence is sufficient to explain God's existence and that perfection necessarily includes this. However, even if we accept that independence is a perfection, this does not fully address the issue, does it? Important questions still remain: What does include mean? What is the actual metaphysic at play here? Does perfection necessitate existence?2 This seems problematic, as nothing can necessitate anything else unless it first exists. Therefore, perfection cannot metaphysically precede existence, assuming these are really distinct attributes. To claim otherwise would involve a form of bootstrapping.
It’s important to note that perfection simply means to be complete or thoroughly made. There are different senses of perfection. In one sense, perfection relates to nature or kind. A perfect cat, for example, would minimally have four legs, since cats, by nature, ought to have four legs. A perfect game of bowling does not have four legs; it has a score of 300. But a score of 300 is not perfective of a cat; it doesn’t even make sense in that context. In another sense, there is absolute or universal perfection, which might involve possessing all possible goodness or any positive aspect that is not inherently limiting (one might think curiosity is a positive aspect, but it is inherently limiting, since it implies some degree of ignorance). However, we don’t know anything like this, at least not directly as we do cats or bowling games, so we are really speculating in the dark about what this absolute perfection might be like—if it exists at all—without a more informative metaphysical framework. Certainly, we don’t know enough to say that this perfect being wouldn’t be simple, where each purely positive property is ultimately just a different aspect of one tightly unified being.3
Now, I’m willing to grant that if something is absolutely perfect, it would be independent. But here’s the problem: perfection itself does not seem to explain such independence. Rather, it seems to be a result of it. So, naturally, my mind turns back to how something could be independent—truly, ontologically independent—in the first place.
Perhaps, then, we might identify perfection and existence as somehow the same. Traditionally, something is perfected to the extent that it has actualized some critical aspect of its nature; thus, perfection is really nothing beyond being itself, making this identification reasonable. However, as soon as we do this, we find ourselves returning to the notion of divine simplicity, or something close to it.
This approach, I think, is much more promising: after all, if we take the traditional route and affirm that God is absolutely simple and purely actual, we have a coherent account of God’s existence and perfection. In this view, perfection is understood as the actualization of a species-specific potential. Things are perfected to the extent that they fully become what they are meant to be, according to their essence. God, being purely actual and whose essence is identical to His existence, is necessarily perfect—He has no potentials left to actualize to become any more excellent than He already is.
Moreover, in the traditional view, because God is unrestricted act, or simply existence itself, He does not possess a limiting essence. Therefore, His perfection is unlimited or absolute, rather than relative to any particular kind. This, I believe, is a much stronger account that rests on more secure metaphysical foundations—namely, what we observe and what the necessary conditions of those realities must be—rather than relying on speculative a priori intuitions about what properties may or may not be great-making.
The result is that it is God’s nature as subsistent existence that explains both His existence and His perfection. This also commits us to divine simplicity.
Anselm of Canterbury, Monologion, chapter 17: "Is it to be inferred, then, that if the supreme Nature is so many goods, it will therefore be compounded of more goods than one? Or is it true, rather, that there are not more goods than one, but a single good described by many names? For, everything which is composite requires for its subsistence the things of which it is compounded, and, indeed, owes to them the fact of its existence, because, whatever it is, it is through these things; and they are not what they are through it, and therefore it is not at all supreme. If, then, that Nature is compounded of more goods than one, all these facts that are true of every composite must be applicable to it. But this impious falsehood the whole cogency of the truth that was shown above refutes and overthrows, through a clear argument."
My analysis assumes not just constituent ontology but that existence is a first-level property. However, notice this: If someone opts instead for some form of Platonism/relational ontology, then simplicity is affirmed anyway, since objects in that ontology are blob-like and intrinsically unstructured.
Again, my intuition tells me simplicity is a perfection: isn’t it better to do more with less complication? Think of improvements in technology and how we often praise advances in simplicity.