Scientism is getting a lot of play these days. It's a difficult word to pin down because it takes on a wide range of meanings depending on who is throwing it around. According to Merriam-Webster online, scientism is:

an exaggerated trust in the efficacy of the methods of natural science applied to all areas of investigation (as in philosophy, the social sciences, and the humanities).

Thus, scientism is the "science can explain everything," (or, at least, "science explains everything important"), kind of position some folks take in arguments about religion, philosophy, the value of the humanities, etc.

Steven Pinker has now waded into the scientism debate with a New Republic essay entitled "Science Is Not Your Enemy: An impassioned plea to neglected novelists, embattled professors, and tenure-less historians." For Pinker there really is no such thing as scientism, which, he claims, is "more of a boo-word than a label for any coherent doctrine."