When Decartes makes the statement about whether heat is the absence of cold or cold is the absence of heat, does he come to a conclusion? Modern science may have a more complex answer to the same question, they might say cold is the absence of motion (molecular motion), and if motion causes heat then you could say that cold is the absence if heat.
I also like the way he uses skepticism in his meditations to find answers and not to just be rebellious like so many skeptics are today. It seems that today they they pose no alternatives to the widely accepted truths, and only destructive things come of it, unlike Decartes search for truth.

I would also like to know what Decartes thought about evolution.