Path integrals are for (a) and (b), but take that with the knowledge that Feynman came up with them maybe 70 or so years ago, so that anything we say about it n

Path integrals are for (a) and (b), but take that with the knowledge that Feynman came up with them maybe 70 or so years ago, so that anything we say about it now tends towards (c) and (d) by virtue of a lot of the (a) and (b) questions already being taken care of.