Combining Texts

Ideas for 'Defending the Axioms', 'Formal and Material Consequence' and 'Meditations'

unexpand these ideas     |    start again     |     choose another area for these texts

display all the ideas for this combination of texts

---

2 ideas

10. Modality / D. Knowledge of Modality / 1. A Priori Necessary

2301	We know by thought that what is done cannot be undone [Descartes]
	Full Idea: Some ideas belong exclusively to the mind, such as perceiving that what has been done cannot be undone, and everything else that is known by the light of nature.
	From: René Descartes (Meditations [1641], §6.82)

10. Modality / D. Knowledge of Modality / 4. Conceivable as Possible / b. Conceivable but impossible

3642	Pythagoras' Theorem doesn't cease to be part of the essence of triangles just because we doubt it [Arnauld on Descartes]
	Full Idea: You can't reason 'I know the triangle is right-angled, but I doubt Pythagoras' Theorem, therefore it does not belong to the essence of right-angled triangles that the square on the hypotenuse is equal to the sum of the squares on the other two sides'.
	From: comment on René Descartes (Meditations [1641], §6.78) by Antoine Arnauld - Objections to 'Meditations' (Fourth) 202