This seems like a good spot to link to one of my favorite essays on the theme you've raised here - the historian and philosopher Isaiah Berlin (of the hedgehog and the fox fame) on "The Concept of Scientific History." (Short version: he argues that there's no such thing). By the way, I'm happy to see such an interesting discussion of my favorite historical topic on HN - thanks.

http://berlin.wolf.ox.ac.uk/published_works/cc/scihist.pdf