Cogito ergo sum

From the Quicksilver Metaweb.

Cogito ergo sum - I think therefore I am. Rene Descartes made this the foundation of his philosophical enterprise, after attempting to jettison from his premises anything at all that could in fact be other than as he found it. If an evil demon could interfere with Descartes' thinking, he reasoned, anything he thought true could be false. In fact, all that one can be sure of is that the mind doing the thinking exists.

However, there are some doubts about the translation -- in some versions of the text "Cogito ergo sum" is replaced with "Cogito sum" -- meaning "I think I am."

The difference in translation is highly significant to the history of ideas, simply because one postits "thought is the base unit of existence" and the other that "existence itself is the base unit." The one is the basic principle that leads directly to Kant's highly structural approach to existence, the other is the basis for the contemporary existential phenomenology of Heiddeger, Sartre and Ponte.

Descartes was not being solipsistic - he was at the beginnings of true philosopical scepticism, which is needed for true science. He did, unfortunately, move on to "prove" that the Christian God was also in existence, and that this, coupled with God's infinite goodness and so on, should reassure us as to the reality of the world.

The famous science fiction scenario of a person trapped in a machine which creates their own personal reality is an example of Descartes' thinking - once called the Brain in a Vat theory, it is now probably better known as "what had happened in The Matrix." However this might be more accurately taken as "I sense, therefore I sim" and is considered by philosophers to be a crude variant of the more powerful and nuanced Simulation Argument.