Full Idea
A proof-theorist could insist that the logical form of a sentence is exhibited by the logical constants that it contains.
Gist of Idea
In proof-theory, logical form is shown by the logical constants
Source
Marcus Rossberg (First-order Logic, 2nd-order, Completeness [2004], §2)
A Reaction
You have to first get to the formal logical constants, rather than the natural language ones. E.g. what is the truth table for 'but'? There is also the matter of the quantifiers and the domain, and distinguishing real objects and predicates from bogus.