I've got an issue with presuppositions with regard to free logic and the supposed circularity (question begging) in Descartes' argument and others like it.

You claim that I think, therefore I am is circular because I think, according to you, presupposes that I am.

I've always been a little confused by conditionals. Take the following two statements:

1. If it rains then the ground will become wet [classic entailment: rain makes the ground wet]

2. If you're relying on arguments to make a point then you endorse the utility of logic in making a point [presupposition: arguments presuppose logic]

Come now to Descartes' argument:

3. I think

Ergo,

4. I am

Is this conditional (I think $\rightarrow$ I am) an entailment or a presupposition? Both? Neither?

Is this conditional (I think → I am) an entailment or a presupposition? Both? Neither? — TheMadFool

An entailment.

Put anther way, in trying to show the validity of "I think therefore I exist" it instead shows that it is circular, that "I think" already supposes that "I exist".

Descartes' argument is valid, but circular. — Banno

An entailment. — Banno

Didn't you say that it was a presupposition?

Perhaps it's both but then that doesn't help, does it?

"I think" is the assumption; "I think" presupposes the thinker.

"I think" is the assumption; "I think" presupposes the thinker. — Banno

To think, there's got to be a thinker. That's why Descartes' argument works. This is, as you said, an entailment.

I would treat the thinker as a necessary condition to be able to say "I think". Are all necessary conditions presuppositions.

My hunch is: all presuppositions are necessary conditions but not all necessary conditions are presuppositions.

think" is the assumption; "I think" presupposes the thinker. — Banno

Which isn't a problem for Descartes' purposes.