File this post under "random quotations". The subject of this quote is the philosophical inquiry into cause and effect. I may have cited the book that the italicized bit below appears in, before in this blog, but I doubt I have referenced this particular passage. The more specific question under discussion is whether "natural selection" is an explanation of evolutionary change: that is, whether it names a cause of which the origin of a new species may be an effect. Suppose that to be a student in a certain classroom R, students must pass a test indicating that they read at the third-grade level. Some students A and B are admitted on the basis of this test, and others C and D are excluded. The use of this test amounts to a selection process, and the existence of this process explains, in one perfectly good respect, why it is true that "All of the students in room R read at the third-grade level." Nonetheless ... the existence of this selection process doe...