It is sometimes said that scientists are divided into "lumpers" and "splitters." The lumper notices that things which seem very different actually have things in common, so they get lumped together (with variable results). The splitter notices that things which seem the same actually have important points of difference, so they make distinctions and split them apart (also with variable results). In general, how we deal with the world as children or as a society is a matter of lumping and splitting. That is how we form concepts in the first place and then go on to form better concepts.
According to the article, what is a "splitter"?
A machine which splits things in two
A scientist
A person who sees the things in common
A person who sees differences in things