Cogito, ergo sum (See CSMK III 159, 161.) Another predecessor was Avicenna's "Floating Man" thought experiment on human self-awareness and self-consciousness. The 8th century Hindu philosopher Adi Shankara wrote in a similar fashion, No one thinks, 'I am not', arguing that one's existence cannot be doubted, as there must be someone there to doubt. The central idea of "cogito, ergo sum" is also the topic of Mandukya Upanishad. Spanish philosopher Gómez Pereira in his 1554 work "De Inmortalitate Animae", published in 1749, wrote ""nosco me aliquid noscere, & quidquid noscit, est, ergo ego sum"" ("I know that I know something, anyone who knows
Cogito, ergo sum and let him deceive me as much as he can, he will never bring it about that I am nothing, so long as I think that I am something. So, after considering everything very thoroughly, I must finally conclude that the proposition, "I am, I exist," is necessarily true whenever it is put forward by me or conceived in my mind. (AT VII 25; CSM II 16–17) There are three important notes to keep in mind here. First, he claims only the certainty of "his own" existence from the first-person point of view — he has not proved the existence