I'm a newbie in advanced mathematics, and I'm trying to understand Godel's theorem. I came across these two words which I couldn't understand clearly.
"Proof Schema" and "Class-Sign" Can anybody provide me definition of these, and describe what these term mean in simple words?
It's from Kurt Godel's book (translated into English) "On Formally Undecidable Propositions of Principia Mathematica and Related Systems".. by Dover publications.. I'll just quote lines where it's introduced (Page No 39)-
"It can be shown that "formula", "proof-schema", and "provable formala" are definable in the system of PM.
Class-Sign: "A formula of PM with just one free variable, and that of the type of natural numbers(class of classes), we shall designate a 'class-sign'..