Question

I saw in your interview with Reuven Seidler that you said there is no really good answer to Hume’s question about the fact that we have no way of knowing that our consciousness is valid with respect to the world, and that the response has to be that we have an intuition that it is in fact valid with respect to the world. What about Descartes’ answer? (I haven’t seen him inside, so maybe that’s not exactly what he said, but in any case I’m talking about the claim itself, and it doesn’t really matter who said it): I think, therefore I exist; I exist, therefore God exists (we won’t get into the whole proof right now); if God exists, then the way I perceive reality is the correct way, because God is good and would not deceive me like that.
This is an answer built on a logical argument and not derived from any basic assumption. Why isn’t that a good argument?