The New "Ghostbusters"

I just read the paperback novelization of the new “Ghostbusters” movie (I still haven’t seen the movie). At one point the author feels she has to address one particularly glaring problem… namely How did they manage to build all this ghostbusting equipment if there had never actually been any evidence of ghosts before this point?
That was kind of the point of the movie, after all, that the Ghostbusters were the first ones to ever prove that ghosts exist, let alone actually capture one. They had PKE meters but they had no idea if they would work or not because in all their investigations, they had never actually encountered a ghost before! So at one point, she had one of the characters say, “Screw empiricism. Let’s try rationalism. In the absence of evidence to the contrary, we assume that ghosts are real and proceed from that as a general rule to test what makes them appear the way they do to us.”
That was the funniest part of the book for me, and probably wasn’t mentioned in the screenplay at all.