 This section explains notation that is not in Principia Mathematica. Except for some notation for “relative” types in \(\ast 63\), and again in early parts of Volume II, there are famously no symbols for types in Principia Mathematica! Sentences are generally to be taken as “typically ambiguous” and so standing for expressions of a whole range of types and so just as there are no individual or predicate constants, there are no particular functions of any specific type. So not only does one not see how to symbolize the argument: