An objection to the Cartesian argument for dualism:
many Theists argue for the existence of the soul (mind, spirit, etc.) cased on a Cartesian argument. They argue as follows:
1. I am known, with certainty to exist (from Descartes)
2. My body is not known, with certainty to exist (also from Descartes)
3. It follows that I exists, but am not my body (from 1 and 2)
4. Therefore, I am my soul
This argument has been around for a very long time, despite being almost childish in its failures of reasoning.
The first problem lies in the simple fact that the conclusion in no way follows from the rest of the argument. We may as well replace 4 with “I am a sentient computer program” or “I am a shoe that thinks”. Both are as useful as what has been offered here.
This is not, however, the greatest objection. The best objection to this argument is that it is fully circular. The Cartesian argument offered is assumes its conclusion. To buy it, you must except that 1 is equal to 2. And yet, 1. may be equal to an unspoken premise:
4. Therefore I am my body.
To see this clearly we can simply restate the argument as such:
1. I am known, with certainty to exist (from Descartes)
2. My soul is not known, with certainty to exist (also from Descartes)
3. It follows that I exists, but am not my body (from 1 and 2)
4. Therefore, I am my body
Seeing it offered this way, it becomes clear that the Cartesian argument for Dualism is useless.
Hope this isn't boring