“If philosophy is about how we see humans, societies the universe and also how we would like them to be, science is just about how they are. One could even say that philosophy collects opinions about facts, when science collects facts about opinions. However, we definitely need also opinions. The opinions that are presented by philosophy can help us to decide what we need to do with the facts that are presented by science.”

-Jaakko J. Wallenius in Being Human -blog(2012)

"I am, therefore I think." I know that that is not what René Descartes said, but the exact opposite of it. However, he did know next to nothing about how the human brain and cognition do really work. If cognition is just brain activity and cognition does produce the brain activity that is sometimes labeled as "mind", there is no need to talk about other things than brain-activity and all other ideas are just empty talk.
I know that there might still be "considerable philosophical debate" over many issues that science has solved a long time ago. This all too often because theists do never give an inch. They just stick to their guns and bring up the old philosophers who did theorize about things on which they had no real data available on their time.

However, now we know so many things better than before. On many things we need not to theorize anymore, but we can have real knowledge. That is true most of all on issues that concern things like human cognition and "mind". However, the old philosophical "theories" are still kept alive, often by people who need them to support their ideology.
Some people really seem to think that there are "philosophical issues" that can be totally removed from the reality. Often they label people who disagree with them "science-believers". This label is given to people who think that philosophy needs to address issues that really are known to exist.

What Descartes did think or did not think about human cognition or "mind" is just not very relevant anymore. We know with extreme certainty that he just did not know what he was talking about when he wrote about the relationship between mind and brain.
Of course, one can take philosophy as a form of crosswords. Then it is not really important how things that are debated relate to the things that we know with great certainty. The level of knowledge concerning the workings of the human brain and cognition was simply just laughable at the time of Descartes. What he uttered based on that knowledge is of historical interest only.

Rene Descartes - Wikipedia

Of course, there are especially Christians who just love to cling to these old ideas that all to often stem from the time of ignorance. They see that can protect their pet ideology with these outdated ideas. However, I just hope that serious followers of philosophy would not fall into that trap anymore.
We just have masses of information concerning that Descartes simply did not have. It is also hardly likely that he would write anything similar is he would be alive today and would have the knowledge that we have now.

After we die, we do live in the memories of others and in our works and deeds that have left their mark in the world. However, there is not a single shred of evidence that any part of consciousness would be left behind after a human’s brain stops working. Brain-activity creates the 'mind', and when there is no brain-activity there is no ' mind'.
The sentence "I am, therefore I think." in the beginning of this piece is from a piece by Michael Shermer that was published in Scientific American. In conclusion, he wrote;

“No one denies that consciousness is a hard problem. But before we reify consciousness to the level of an independent agency capable of creating its own reality, let's give the hypotheses we do have for how brains create mind more time. Because we know for a fact that measurable consciousness dies when the brain dies, until proved otherwise, the default hypothesis must be that brains cause consciousness. I am, therefore I think.”

Michael Shermer in: http://www.scientificamerican.com/article.cfm?id=what-happens-to-consciousness-when-we-die