Descartes's argument for separability of mind and body

Descartes’s argument for the separability of mind and body relies on the existence of God (which he proves earlier in the Meditations).

• If $p$ could be clearly and distinctly understood, then God could make it so that $p$.
• If $p$ could be clearly and distinctly understood without $q$, then God could have made it so that $p\wedge \neg q$.
• If God could have made $p$ without $q$, then $p$ and $q$ are distinct.
• Mind and body can be clearly and distinctly understood without each other.