Surely this individual Cartesian actors would pursue their rational self interest, and over time, arrive at TRUTH. Praise be the new god!
But of course, it all breaks down for similar reasons. People actually aren't that, and trying to derive human behaviour from Newtonian mechanics is a very silly thing to do. You aren't really a rational mind-soul existing atemporally floating in a Cartesian vacuum of free space, and neither is your neighbour.
Act like a damn human, you are one.