Add link to blog post addressing common objections

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: thiagoa

README.md

@@ -40,6 +40,9 @@ catches that immediately and reports clear, precise error messages
 showing exactly which signatures diverged — keeping your classes
 aligned as the design changes.
 
+For a deeper discussion of the tradeoffs and common objections,
+see [Why Duck Typer?](https://thoughtbot.com/blog/why-duck-typer).
+
 ## Installation
 
 Add to your Gemfile: