whats the difference between Purism and Minimalism?

i think you're right inasmuch as most movements borrow heavily from the one before, and the stages of modernism were no exception to this. as you say, purism was about using abstracted (or non-abstracted) geometric and mechanical forms, but there wasn't a huge concern about the clashing of volume - in fact, often these were celebrated (curves meeting rectilinear forms). in minimalism, the whole dialogue is much more pared down (as the name suggests) - its reduction, unified space, less is more, less structure, fewer but more significant forms, cleaner interfaces / junctions. that would be my first off the cuff response.

never herd of them, but i'd think it's just like Gothic architecture, Normal Architecture and Romanesques architecture .. not very clear margin between them styles but people say they are different, yet there are buildings built with cross style and relations ... only very small difference between them i guess..