6
votes
2answers
182 views

Symbols and terminology for distinguishing derivability from sequents

First some definitions to make it clear what I'm talking about: A deductive system is a set $J$ of judgments together with a set $R$ of inference rules each of the form $$ j_0 \leftarrow j_1, ...
3
votes
2answers
181 views

Stronger condition lead to weaker result?

Suppose there are two theorems $A \Rightarrow B$ and $C \Rightarrow A$. Then we have $C \Rightarrow B$. Now comparing $A \Rightarrow B$ and $C \Rightarrow B$, we know that $C \Rightarrow A$ means C ...