Antoine Léonard Thomas (1 October 1732 – 17 September 1785) was a French poet and literary critic, best known in his time for his great eloquence, especially for éloges in praise of past luminaries. It was in recognition of this that he was elected to Académie Française.^[1]

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In an award-winning 1765 essay in praise of René Descartes, he penned a fuller form of the cogito in French as "Puisque je doute, je pense; puisque je pense, j'existe." With rearrangement and compaction, the passage translates to "I doubt, therefore I think, therefore I am," or in Latin, "dubito, ergo cogito, ergo sum."^{[lower-alpha 1]}

He was born in Clermont-Ferrand and died aged 52 in Oullins.

• Eloge de René Descartes (in French). Yverdon. 1765.