The Yamaka (Pairs) consists of ten chapters on different topics, starting with the roots of wholesome or unwholesome conduct. It applies a series of pairs of questions, with the object of fully determining the scope of application of terms. For example, are all rūpa (physical phenomena) part of the aggregate of physical phenomena? No, because there are idiomatic uses of rūpa such as evarūpa (“of such a sort”). But are all instances of the aggregate of physical phenomena? Yes.