Full Idea
In real-life reasoning it is the semantic content that guarantees the validity of the inference, not the syntactical rule.
Clarification
'Semantics' is meanings, 'syntax' is sentence structure
Gist of Idea
In real reasoning semantics gives validity, not syntax
Source
John Searle (Rationality in Action [2001], Ch.1.II)
Book Reference
Searle,John R.: 'Rationality in Action' [MIT 2001], p.21