En réponse à Henrik Theiling :

> > it is just a basical law of logic. If you deny it,
> > then you cannot build any logic any more.
>But could the original sentence not also mean that it causes being?
>What would being without thinking for a human be?  Would it be being?
>I think it's more than just an implication.
>It's hard to keep the sentence underspecified if you have too many
>cases... :-)

Actually, if you read Descartes (in the original Latin) you'll discover 
that the sentence he wrote doesn't contain a "therefore", nor any other 
connector for that matter. It is "I think, I am", *not* "I think, therefore 
I am" (a common mistranslation that was already common in his time, and 
that he fought against all his life). The sentence is *not* a law of logic. 
It is *not* an implication, it is *not* a cause-and-effect description. The 
sentence is a declaration of *EQUALITY*: I think = I am. It's the ultimate, 
undoubtable foundation of a philosophy based on getting rid on anything 
doubtable in order to find a solid foundation. The ego can't doubt its own 
existence for the simple reason that it is doing the thinking, the 
doubting, at the very moment it tries to doubt it, and reciprocally the ego 
exists as a purely thinking being, because anything else (the body, the 
sensations, etc...) have been doubted away (not because they don't exist, 
but because there is no proof, at the current level of thought, that they 
are more than mirages. The basis for Cartesianism is pure skeptism).

So to your question "what would being without thinking for a human be?", in 
the Cartesian philosophy it would be a contradiction in terms, at least for 
the ego. In the Cartesian philosophy, thinking and being are synonymous 
*for EGO*. For whatever could exist besides ego (which Descartes spends the 
remaining five of his six metaphysical meditations trying to find out, 
unconvincingly in my opinion), thinking and being are different things. And 
things besides ego can exist without thinking. But for EGO itself, thinking 
and being are synonymous. That's what the "cogito, sum" (the correct quote) 

Christophe Grandsire.

You need a straight mind to invent a twisted conlang.