The noted and highly respected pluralist, Dr. Richard Mckeon, in his introductory comments to the International Institute of Philosophy's 'Entretiens in Jerusalem, in 1977, quotes from Descartes response to the second objections in the Meditations. McKeon;'Descartes contends that he distinguishes two things in the writing of the geometers, the order (ordo) and the reasoning (ratio) of demonstrating. There are two ways... by analysis or resolution or by synthesis or composition. Descartes; "Analysis shows the true way by which a thing is discovered (inventa) methodically and as it were a priori, [French version translates a priori by 'shows how effects depend on causes'], so that, Des.; "if the reader wishes to follow it and pay attention to all that it contains, he will understand the thing demonstrated no less perfectly and will make it no less his own than if he had discovered it himself." McKeon; 'This way of demonstration will not convince obstinate or inattentive readers.' It would be an understatement to say that this left my mind boonswaggled. There is more to this presentation but perhaps this enough to ask; How does this square with and does it in any way affect the current usage of a priori?

Richard McKeon (/məˈkiːən/; April 26, 1900 – March 31, 1985) was an American philosopher and longtime professor at the University of Chicago. His ideas formed the basis for the UN's Universal Declaration of Human Rights. If there is not enough info here I can complete Descartes response with his response concerning a posteriori. Charles M. Saunders

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    This is the archaic use from medieval scholastics. From Online Etymology Dictionary:""from cause to effect," a Latin term in logic from c. 1300, in reference to reasoning from antecedent to consequent, based on causes and first principles, literally "from what comes first," from priori, ablative of prior "first". Opposed to a posteriori.". Modern use derives from Kant and has a different meaning, hence the rephrasing in the French translation.
    – Conifold
    Commented Jan 26, 2020 at 13:17
  • It would be interesting to understand why the change occurred and whether it was the correct interpretation or whether Kant misinterpreted and created a superficial distinction. CMS
    – user37981
    Commented Jan 27, 2020 at 12:43
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    Kant did not care to interpret, he simply disregarded the old usage, and not just on this. He nearly reversed the old usage of subject/object, for example, his "matter", "realism", etc., were of his own making too. To him, pre-critical philosophy was largely a failure to be replaced, and old words to be filled with new meanings to do so.
    – Conifold
    Commented Jan 27, 2020 at 12:58
  • Too bad; since it's clear that the marvelous mind of Kant has left all who follow him in a state of veritable warfare over what he meant by what; perhaps it would have been best if he'd left well enough alone. This does not diminish his importance or genius, it only marks what I believe is a relevant criticism. Epistemology has gained nothing by employing his distinctions. CMS
    – user37981
    Commented Jan 28, 2020 at 13:09

1 Answer 1


As Conifold points out, Descartes' use of 'a priori' doesn't fit with modern usage:

Descartes' use of the term a priori here seems to correspond neither with the modern, post-Leibnizian sense (where a priori truths are those that are known independently of experience), nor with the medieval Thomist sense (where a priori reasoning is that which proceeds from cause to effect). What Descartes may mean when he says that analysis proceeds 'as it were a priori' (tanquam a priori) is that it starts from what is epistemically prior, i.e. from what is prior in the 'order of discovery' followed by the mediator.

The Philosophical Writings of Descartes, ed. J. Cottingham et al., II, Cambridge: CUP, 2008: 110, fn. 2.

Cottingham translates the relevant Reply text as follows:

Analysis shows the true way by means of which the thing in question was discovered methodically and as it were a priori, so that if the reader is willing to follow it and give sufficient attention to all points, he will make the thing his own and understand it just as perfectly as if he had discovered it for himnself. (II: 119.)

  • Thanks for the acceptable answer and its clarity. Do you know why Kant would altered this useful and quite fascinating definition of the two opposing terms and shift a priori into only a state of mind? CMS
    – user37981
    Commented Jan 27, 2020 at 12:46
  • Thanks for comment. I could formulate an answer but would not be sure of its accuracy. Why not ask about the Kantian a priori in a separate question? Best - GLT
    – Geoffrey Thomas
    Commented Jan 27, 2020 at 12:56

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