"Google is replacing PageRank with RankBrain and when this is complete they won’t know why certain pages are offered as the best result"<p>I'm not sure if this will always be true. I think that if we move toward a sort of neural network programming (1) we won't be able to "know why" in the sense that we can explain the functions, but will instead explain programs based on output from the layers and from the relationships between variables. For instance, deep dream<i></i> is a way to understand how google's image classifier is "working" (2). It's super interesting that the classifier thinks that a human arm is part of a dumbbell, for instance.<p>1) Maybe something like this: <a href="http://web.mit.edu/~axch/www/art.pdf" rel="nofollow">http://web.mit.edu/~axch/www/art.pdf</a>.<p>2) <a href="http://googleresearch.blogspot.ch/2015/06/inceptionism-going-deeper-into-neural.html" rel="nofollow">http://googleresearch.blogspot.ch/2015/06/inceptionism-going...</a>