Good sense is of all things in the world the most equally distributed, for everybody thinks he is so well supplied with it, that even those most difficult to please in all other matters never desire more of it than they already possess.

[Le bon sens est la chose du monde la mieux partagée; car chacun pense en être si bien pourvu, que ceux même qui sont les plus difficiles à contenter en toute autre chose n’ont point coutume d’en désirer plus qu’ils en ont.]

René Descartes (1596-1650) French philosopher, mathematician
Discourse on Method [Discours de la méthode], Part 1, Opening Words (1637) [tr. Haldane & Ross (1911)]
    (Source)


(Source (French)). Alternate translations:

Right understanding is the most equally divided thing in the World; for every one beleevs himself so well stor’d with it, that even those who in all other things are the hardest to be pleas’d, seldom desire more of it then they have.
[Newcombe ed. (1649)]

Good sense is, of all things among men, the most equally distributed; for every one thinks himself so abundantly provided with it, that those even who are the most difficult to satisfy in everything else, do not usually desire a larger measure of this quality than they already possess.
[tr. Veitch (1850)]

Good sense is the most fairly distributed thing in the world; for everyone thinks himself so well supplied with it, that even those who are hardest ot satisfy in every other way do not usually desire more of it than they already have.
[tr. Ascombe & Geach (1971)]

Good sense is the best distributed thing in the world: for everyone thinks himself so well endowed with it that even those who are hardest to please in everything else do not usually desire more of it than they possess.
[tr. Cottingham, Stoothoff (1985), sec. 1]

Common sense is the best distributed commodity in the world, for every man is convinced that he is well supplied with it.
[Oxford Reference]

Of all things, good sense is the most fairly distributed: everyone thinks he is so well supplied with it that even those who are the hardest to satisfy in every other respect never desire more of it than they already have.

Nothing is more fairly distributed than common sense: no one thinks he needs more of it than he already has.