MA, ul's words are certainly right and true. With that and your signature, I am drawn to Descartes words concerning this issue =
"But I have convinced myself that there is absolutely nothing in the world, no sky, no earth, no minds, no bodies. Does it now follow that I too do not exist?
No: if I convinced myself of something [or thought anything at all] then I certainly existed. But there is a deceiver of supreme power and cunning who is deliberately and constantly deceiving me. In that case I too undoubtedly exist, if he is deceiving me; 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."
The above psychology - in red - is the premise of the book - 'Catch 22' by Joseph Heller - of which the movie and the book are in my library and some of my favorite stuff.