The Philosophical Bend of Mathematics

Quine thought that the text surrounding Principia Mathematica was kind of sloppy and inelegant. This was also the heyday of behaviorism. Quine, just like if you were doing regular natural science, you don't want to posit extra types of entities if you don't need to. He certainly was of the bent that if he could only talk about physical things and not talk about irreducibly mental objects, he was definitely in favor of that.