Descartes and the Causal Principle: talking relics

Linda asks:

“Now it is indeed evident by the light of nature that there must be at least as much (reality) in the efficient and total cause as there is in the effect of that same cause. For whence, I ask, could an effect get its reality, if not from its cause? And how could the cause give the reality to the effect, unless it, also, possessed that reality? Hence it follows that something cannot come into being from out of nothing, and also that what is more perfect (that is, what contains in itself more reality) cannot come into being from what is less perfect.”

What is Descartes arguing in the text above? In other words, what does this quote mean? I am having a hard time understanding his point.

Answer by Craig Skinner

You are having a hard time because Descartes is talking relics. Of medieval scholastic philosophy that is.

We read Descartes in modern english translations, which has the effect of making him seem more modern than, say, Locke or Hume whom we read in their original texts. Try reading Molyneux’s (1680) english translation of Meditations and you will see this. But, although determined to shake off scholasticism and “build anew from the foundations”, Descartes was steeped in it, and the passage you quote is an example.

It occurs in M3 where Descartes sets out his causal argument for the existence of God. This relies on the scholastic “Causal Principle” which roughly says that the cause must be greater (or at least as great) as the effect, never the reverse. So Descartes will go on to argue that since he has a clear and distinct idea of a perfect, infinite being (God), such an idea with perfect and infinite content could only be produced by a cause with perfect and infinite reality (not puny finite me), namely God, so God exists. Actually the details are more subtle and hard to grasp: the existence of something (its formal reality) is distinguished from its content (objective reality), and reality comes in degrees (infinite substance, finite substance, modification of a substance), so that the argument strictly is that the degree of formal reality of the cause must be at least as great as the objective reality of the effect.

We can reject his argument on a number of grounds: deny I have any idea of an infinite being; agree I have this idea but say that it’s my own, a reasonable extrapolation from thinking of something getting bigger and bigger without limit; deny the causal principle (no evidence/argument given for it).

And so, a reasonable simplified paraphrase of the passage is:

“It stands to reason that a cause must be at least as great as its effect. Otherwise how could it produce the effect. It follows that we cant get something from nothing, or the perfect from the imperfect”

Finally, whilst some scholastic ideas do show unnecessary nitpicking and logic-chopping, and can be quietly forgotten, I dont share Descartes’ wholesale rejection. On the contrary, the Aristotelian/scholastic metaphysics framework of substance/form, essence/attributes, actual/potential, and efficient/final causes finds increasing acceptance in modern metaphysics, biology, cosmology and philosophy of mind. Here Descartes sets us off on the wrong foot (again, his dualism is another example). But he is still a great philosopher, great mathematician, considerable scientist, and one of my favourites.

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