Full Idea
Soundness theorems are seldom very informative, since typically we use informally, in proving the theorem, the very same rules whose soundness we are attempting to establish.
Gist of Idea
Soundness theorems are uninformative, because they rely on soundness in their proofs
Source
Vann McGee (Logical Consequence [2014], 5)
Book Reference
'Bloomsbury Companion to Philosophical Logic', ed/tr. Horsten,L/Pettigrew,R [Bloomsbury 2014], p.40
A Reaction
[He cites Quine 1935]