If you would be a real seeker after truth, it is necessary that at least once in your life you doubt, as far as possible, all things.
[Veritatem inquirenti, semel in vita de omnibus, quantum fieri potest, esse dubitandum.]
René Descartes (1596-1650) French philosopher, mathematician
Principles of Philosophy [Principia Philosophiae], Part 1 “The Principles of Human Knowledge [De Principiis Cognitionis Humane],” Article 1 (1644)
Common, unsourced translation of Descartes first principle. Frequently mis-sourced to Discourse on Method (1637) or Meditations on First Philosophy (1641), though those predecessor works do speak of the same principle.
(Source (Latin)). Alternate translations:
That in order to seek truth, it is necessary once in the course of our life, to doubt, as far as possible, of all things.
[tr. Veitch (1850)]
That in order to examine into the truth, it is necessary once on one's life to doubt of all things, so far as this is possible.
[tr. Haldane/Ross (1934)]
The seeker after truth must, once in the course of his life, doubt everything, as far as possible.
[tr. Miller & Miller (1982)]
That whoever is searching after truth must, once in his life, doubt all things; insofar as this is possible.
[tr. Cottingham/Stoothoff/Murdoch (1985)]
