On a tangent note, Descartes famous "cogito ergo sum" ("I think therefore I am") falls into the trap of the grammar: it presupposes that the thinker, who does t

On a tangent note, Descartes famous "cogito ergo sum" ("I think therefore I am") falls into the trap of the grammar: it presupposes that the thinker, who does the act of thinking, exists. The actually undeniable empirical statement would be "cogitationes sunt", "thoughts exist", but you can't get anywhere from that without answering additional questions: for example, do the thoughts need a thinker (whatever it may be) to exist and think them, or?.. If you answer "yes", you can follow Descartes' line of reasoning. If you answer "no", no problem, there is a whole philosophical tradition of Buddhism built on that.