 Here are some intuitive ways to understand the definition of type. Suppose that “Socrates” names an individual. (We are here ignoring Russell’s considered opinion that such ordinary individuals are in fact classes of classes of sense data, and so of a much higher type.) Then the individual constant “Socrates” would be of type \(\iota\). A monadic propositional function which takes individuals as arguments is of type \((\iota)\). Suppose that “is mortal” is a predicate expressing a property of individuals. The function “\(\hat{x}\) is mortal” will be of the type \((\iota)\). A two-place or binary relation between individuals is of type \((\iota,\iota)\). Thus, a relation expression like “parent of” and the function “\(\hat{x}\) is a parent of \(\hat{z}\)” will be of type \((\iota,\iota)\). 