DESCARTES: MEDITATION 3
Preliminaries. The broad outlines of the argumentative strategy for this meditation and the next
is laid out here. The Meditator now seeks a criterion to go on with: a rule that will allow
him to decide what is certainly true. (I’ll gloss text by referring to each paragraph numbered
sequentially from the start of the Third Meditation.) The Meditator begins by reviewing his
progress in 3.01: he is a thing that thinks, and, even if his senations and imaginations “may have
no existence outside me,” he is certain that these modes of thinking qua modes “do exist within
me.” So far so good. The Problem of the Criterion is introduced in 3.02. Since the Meditator
is certain he is a thinking thing, he asks whether he also knows what is required to be certain
of something. The only thing he has to go on is “a clear and distinct perception” that he is a
thinking thing, but that seems good enough; he concludes at the end of 3.02:
So I seem now to be able to lay it down as a general rule that whatever I perceive very
clearly and distinctly is true.
The Meditator then raises doubts about the Clarity-and-Distinctness Rule (hereafter CDR), on
the grounds that he seemed to clearly and distinctly know things about which he was able to
raise metaphysical doubt. This doubt was eventually based on a possibility (3.04):
Indeed, the only reason for my later judgment that they were open to doubt was that
it occurred to me that perhaps some God could have given me a nature such that I was
deceived even in matters which seemed most evident.
The Meditator ﬁnds this hypothesis hard to sustain: (i) the few examples he has of clear and
distinct truths are entirely persuasive; (ii) he has no reason to think there is a deceptive God, or
for that matter a God. There follows a crucial passage at the end of 3.04:
But in order to remove even this slight reason for doubt, as soon as the opportunity
arises I must examine whether there is a God, and, if there is, whether He can be
a deceiver. For if I do not know this, it seems that I can never be quite certain of
The Meditator, then, wants to establish the existence of a non-deceptive Deity in order to...
what? Two different answers spring to mind: (a) to rule out the reason for doubting based on
the Deceptive-Deity-hypothesis; (b) to validate CDR. Now (a) and (b) are equivalent under the
assumption that the DD-hypothesis is the only reason to doubt CDR. Here we go!
THE MEDITATOR’S PROOF OF THE EXISTENCE OF GOD
To prove: God exists.
The proof of God’s existence here is a causal proof: it begins from facts about what there is
and infers the existence of God as the (only possible) cause of the facts. The Meditator begins
obliquely, by considering how truth and falsehood can arise in the understanding—presumably
because it is only in these cases that “deception” has a foothold. This point emerges from the
discussion and isn’t stated as such. Rather, we begin with a distinction:
(1) Some ideas are simple and others complex (3.05).
Descartes’s way of putting this point is hopeless: he says that some thoughts are like “images of things” and others “have various additional forms.” What he means is that ideas in the strict
sense have only putative representational content, whereas other mental phenomena—volitions,
emotions, judgments—have something in addition to putative representational content.
(2) Simple ideas are not true or false as such (3.06).
Descartes will eventually qualify (2) with his doctrine of ‘material falsity’, but for now he is
content with the point that ideas qua ideas are just so much thinking.
(3) Complex ideas that are volitions or emotions are not true or false as such (3.06).
The nonexistence of their objects does not invalidate volitions or emotions from being “about”
the things they are about: a desire for a unicorn is no less a desire than (say) my desire for the
breadcrust before me. The Meditator concludes:
(4) Truth and falsity pertain primarily to judgments (3.06).
The proof of (4) is by disjunction-elimination. Falsehood crops up in the following way:
(5) Judging that “the ideas which are in me resemble, or conform to, things located outside
me” is the “chief and most common mistake” in judgments (3.06).
The Meditator here assumes a stronger claim, namely:
(5*) The existential error sketched in (5) is the only way falsehood enters into judgments.
(At least we never hear of any other way.) The replacement of (5) by (5*) explains why the
argument suddenly changes direction to look at the possible causes of the ideas one has, with the
eventual aim of returning to their liability to existential error. This move, of course, presupposes
(6) Ideas are caused.
Now (6) has two distinct readings in light of the later distinction between formal and objective
being, and the Meditator endorses both (although it is only plausible for the former):
(7) Ideas as formal beings are caused.
(8) Ideas as objective beings are caused.
We’ll come back to this point. Given that ideas (in either sense) are caused, we can inquire about
their causal origin. The Meditator proposes a trichotomy:
(9) Ideas are either innate, adventitious, or invented by me (3.07).
This is, apparently, an exclusive and exhaustive division, and the Meditator is careful to state
that for all he knows his ideas are all of one kind or another; he gives examples of each. The
next several paragraphs are devoted to the possibility of error in adventitious ideas (3.08–11).
Presumably the Meditator isn’t tempted to believe that ideas he produces actually “resemble”
anything in the external world. It’s a little harder to see why innate ideas are bypassed. One
possibility is that the Meditator’s examples—“what a thing is, what truth is, and what thought
is”—might be considered devoid of putative representational content; at least, I can’t ﬁnd a better
reason. We then get a brief argument that although adventitious ideas, i.e. ideas the Meditator
believes “to be derived from things existing outside me,” don’t support the conclusion that they
are so derived and accurately represent the items from which they are derived. The grounds
for thinking that such adventitious ideas do accurately represent external things (3.08): (a) the
Meditator has been so taught by Nature; (b) they do not depend on the Meditator’s will; (c) “the most obvious judgment” for the Meditator to make is that “the thing in question transmits to
me its own likeness rather than something else.” But there are clear objections to each:
• Against (a): This is no more than a spontaneous impulse to believe the claim, not a reason
for doing so (3.09). Here we get a contrast with the “light of nature” a.k.a “the natural light (of
• Against (b): Being independent of the Meditator’s will isn’t sufﬁcient grounds to conclude that
the source of these ideas is outside the Meditator, since they could be generated by “some other
faculty” within the Meditator (3.10).
• Against (c): Even if ideas are generated by external items it doesn’t follow that they resemble
those items—as instanced by the sensory and astronomical ideas of the Sun (3.11). (At least one
of these ideas has to be wrong.)
Well, that seems to shut down this line of inquiry (3.12). But the Meditator brings in a pair of
deﬁnitions (3.13) and a causal principle (3.14) to help him out.
(10) Formal reality = df The reality possessed by something in virtue of what it is.
Descartes needs only an ordinal ranking that might be ultimately grounded on the kind of
existential dependence involved (where the ranking is given with respect to formal reality):
(11) substances ≻ mfres ≻ accidfrts
The second deﬁnition is:
(12) Objective reality = df The reality possessed by something representational—perhaps qua
representing what i