Descartes' argument for god includes his idea of "objective reality", id est, clear and distinct perception implies existence. Considering his own scientific bent of mind, I'm curious to know what he thought about phenomena such as mirages, refraction, or perhaps stuff like gravity hills. What did he mean by "clear and distinct"?

(Descartes' time was pre-Newton and therefore before modern optics.)


2 Answers 2


Descartes clear and distinct perception means several things. Its not simply about vision, but also the intellect.

Numbers can be seen clearly and distinctly in the intellect; though of course they have no bodily forms. Recall Descartes cogito allows him to build up his epistmology from intellect, or the ego.

Mirages are clearly & distinctly seen for what they are; evanascent forms.

Similarly refraction.

The actual mechanism of why they are as they are; their physical properties is a question of an empirical science; and not of his philosophy.

  • Thank you. Does that then imply that Descartes was able to see his god clearly and distinctly in his intellect? Isn't he simply hypothesising the existence of a perfect being? Commented Dec 26, 2013 at 10:07
  • That, I'm not sure about - which is why it wasn't in my answer; but I'd say it was a plausible yes - simply because Spinoza went on from Descarte and he did exactly that. Commented Dec 26, 2013 at 13:30
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    There is more to it, though; the starting point that Spinoza takes are ideas such as existence, essence & substance. One supposes that these are the clear & distinct ideas that Spinoza uses in his geometric method. His God follows. But, if one follows the pereginations of mathematical thought, it doesn't develop in a strict logical manner as one sees laid out in text-books, but is more organic & coherentist. So its highly plausible that Spinoza had a belief in God, reflected on his nature, until those ideas became clear & distinct, and placed them in a geometric method. Commented Dec 28, 2013 at 7:59
  • One might suppose Descartes case was similar. Finally, what can it mean to see God clearly and distinctly? I suggest that it means to see the idea of God, not God himself. The Islamic sufi tradition try to rend away that final veil to reveal the hidden. Commented Dec 28, 2013 at 8:08

If your hallucination was clear and distinct would that then also imply existence? Also the possibility that a deity exist and the perception being unclear is also possible. Why would the lack of perception have any influence of anything existence? Also a lot of molecules / atoms where perfectly happy in existence before humanity developed the tool to perceive them how would the perception = existence hypothesis account for them.

You could have invisible things that exist. You could have visible things that do not exist. You could have visible things that exist. You can also have invisble things that do not exist.

At the very least a deity is under no obligation to make himself known to anyone in any manner than the one he chooses. You could also make the case that he has chosen to make himself abundantly "known" to a select few people like the ones in the Bible and now asks you to take the accounts they have left us all as a testament to his existence.

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