Full Idea
Wittgenstein's by-product theory is that the meanings of the logical constants are conveyed by their introduction rules, and these rules have as a by-product the class of logical truths.
Gist of Idea
Logical truths are just 'by-products' of the introduction rules for logical constants
Source
report of Ludwig Wittgenstein (Tractatus Logico-Philosophicus [1921]) by Ian Hacking - What is Logic? §03
Book Reference
'A Philosophical Companion to First-Order Logic', ed/tr. Hughes,R.I.G. [Hackett 1993], p.228
A Reaction
I find this approach highly plausible. All the truths about chess openings are just a by-product of the original rules.