(β) A propositional function is necessary when all its values are true.
Call it a propositional function; and, if φx be a propositional function, the undetermined variable x is the argument.
Now consider a propositional function Fχ in which the variable argument χ is itself a propositional function.
A 'propositional function' or 'norm' may be 'non-predicative.'
A propositional function (that is to say a definition) does not always determine a class.
For the text is rather a vague symbolical expression of a propositional function which is asserted to be true at all instants.