 To illustrate these various doctrines for various targets and units, let the target \(t_1 =\) concrete objects, and let the unit \(u_1 =\) highest type. To be a monist for \(t_1\) counted by \(u_1\) is to hold that concrete objects fall under one highest type. The materialist, idealist, and neutral monist are all monists of this sort (substance monism). They all agree that concrete objects fall under one highest type, disagreeing only over whether the one highest type is material, mental, or something deeper.