Is Descartes just proving what we already know, or have we discovered something important on this journey from doubt to absolute certainty?

Descartes Meditations

So Descartes spends the whole time in this book, which you’ve now finished reading, trying to prove two simple things and one not-so-simple (rather huge) thing.

But at the end of the day, do you think that Descartes achieves his goals?

Is Descartes just proving what we already know, or have we discovered something important on this journey from doubt to absolute certainty?