I'm currently writing a paper on Descartes argument for God based on his third meditation. One premise of the argument that seems fairly important is the claim that "no effect can be greater than its cause". Putting aside how Descartes can know this on his own epistemology, have there been any strictly logical arguments made for this position? Or are the arguments generally made from induction?

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    Descartes is using a concept from medieval philosophers sometimes called proportionate causality. It is rather obsolete and does not accord with how we thing of causes and effects in modern science. Edward Feser is an example of a modern writer in the Aristotelian tradition who makes use of the distinction in his book, Five Proofs of the Existence of God. Other than that, it is not commonly used today.
    – Bumble
    Nov 29, 2023 at 18:35
  • @Bumble is proportionate causality the result of a strict logical necessity? Has this concept been replaced by the PSR? Or does the PSR contain proportionate causality within itself in some respect?
    – Luke Hill
    Nov 29, 2023 at 18:39
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    The concept of proportionate causality is not a purely logical principle and it has pretty much died out in modern philosophy. There is not much to recommend it. Things do not have degrees of reality or greatness as Descartes would have it.
    – Bumble
    Nov 29, 2023 at 20:19
  • See Lloyd, The Principle That the Cause Is Greater than Its Effect, who reconstructs some arguments for it from Aristotle, Plotinus, Aquinas, Descartes, etc., e.g. Aristotle:"the formation of that which is potentially is brought about by that which is in actuality". Lloyd's surmise:"we have a notion of causation as the transferring or transmitting of some property from one thing to another. It is the notion which accounts for the Scholastic principle in Descartes' thinking... He regards it as logically equivalent to 'a nihilo nihil fit'".
    – Conifold
    Nov 29, 2023 at 23:58
  • I wonder if the notion that the cause has to be more complex than the effect is a descendent of this notion. It would ironic because that principle is typically used to argue against God. Nov 30, 2023 at 1:55

2 Answers 2


I assume that the passage you rephrase as Descartes’ claim “no effect can be greater than its cause” is

Iam vero lumine naturali manifestum est tantundem ad minimum esse debere in causa efficiente et totali, quantum esse in eiusdem causae effectu; nam quaeso, undenam posset assumere realitatem suam effectus, nisi a causa? (Med III. 14)

Now, it is manifest by the natural light that there must at least be as much reality in the efficient and total cause as in its effect; for whence can the effect draw its reality if not from its cause?

The crucial word is the Latin “tantundem (= as much than)” which refers to the term “realitas objectiva (= objective reality)” in the passage just before the quote. Hence your question reads:

How to argue that the cause has at least as much objective reality than the effect?

Descartes does not speak about the relation between cause and effect if both are physical events or material objects. Descartes speaks about the relation between ideas. In the section before he conludes that his idea of God can only origin from an idea which has equal or even more objective reality:

[…] illa [idea], per quam summum aliquem Deum, aeternum, infinitum, omniscium, omnipotentem rerumque omnium, quae preaeter ipsum sunt, creatorem intelligo, plus profecto realitatis objectivae in se habet quam illae, per quas finitae substantiae exhiberunt. (Med III.13)

[…] the idea by which I conceive a God [sovereign], eternal, infinite, [immutable], all-knowing, all-powerful, and the creator of all things that are out of himself, this, I say, has certainly in it more objective reality than those ideas by which finite substances are represented.

Now Descartes has to argue why the existence of the God-idea in his mind, being the effect, implies that the God-idea has a referent as its cause, i.e. that God exists. That’s the content of the rest of the meditation and it seems to me the proper problem.

In my opinion Descartes attempts to derive his solution from the meaning of the technical term realitas objectiva. But that requires to dive deeply into scholastic ontology and the scholastic principles of argumentation. It’s not enough to consider only the new principles introduced by Descartes’ epistemology - it's not an easy task.


I know next to nothing about Descartes, so I will trust Jo Wehler's answer to be the correct one. As an aside, you might want to consider a parallel with the principle of conservation of energy in physics, combined with the fact that no process is 100% efficient. That tells you in a different sense that the magnitude of effects, when quantified in a very narrow way purely in terms of energy, cannot be greater than their causes. Here you have to take a holistic view of what the causes are. For example, if I illuminate the tasteless facade of my billion-dollar mansion, you might say that the effect of countless gazillions of photons bouncing off the building and into space is greater than the cause, if you consider the cause to be my lazy flick of a switch that triggered the thousands of floodlights to blaze. However, if you take a broader view that the cause of the blazing light includes half the output of my local power-station, then you will see that the causes do indeed exceed the effects.

  • To build on what you're saying from a theistic view; what's the cause of a nuclear explosion? The shaped charges in a nuke pale in comparison to the mushroom cloud, like your light switch analogy. So what's the greater cause? What's the origin of the energy in your coal, or my uranium? We quickly end up back into the First Mover argument. The greater causes all have greater causes of their own, chaining up to a Prime Cause of seemingly limitless capacity. Nov 29, 2023 at 23:37
  • @ConnieMnemonic indeed. The nuclear explosion is the consequence of potential energy in the Uranium. Where did that energy come from? Nuclear reactions in stars. Where did that energy come from? Etc etc. Ultimately you trace back to the Big Bang. Nov 30, 2023 at 6:42
  • And then you're still stuck with "what caused the big bang?" But that's a whole other discussion, heh. Nov 30, 2023 at 8:44
  • @ConnieMnemonic indeed again! And if you don't mind my prying, why do you call yourself ConnieMnemonic? Nov 30, 2023 at 9:09
  • Not at all! I picked this name as it's a mutation of "Johnny Mnemonic" that fits my real name slightly closer. I'm a huge fan of sci-fi and cyberpunk, and William Gibson wrote a book called "Johnny Mnemonic" which is a little out there, heh. Loved his other stuff, though I'm actually more of a Philip K. Dick fan :) Nov 30, 2023 at 9:41

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