diff --git a/PRINCIPLES.md b/PRINCIPLES.md
index 34b9327..e41133c 100644
--- a/PRINCIPLES.md
+++ b/PRINCIPLES.md
@@ -37,6 +37,7 @@
 * [Stuart Sierra](https://twitter.com/stuartsierra/statuses/516967544167489536) - "Bugs are dependency-transitive"
 * [Stuart Halloway](https://twitter.com/stuarthalloway/statuses/502906568569286657) - the #1 source of software defects is easy presumtion. Presume nothing.
 * "The Principle of Least Astonishment: Make a user interface as consistent and as predictable as possible"
+* "Worried that TDD will slow down your programmers? Don't. They probably need slowing down." [J. B. Rainsberger](https://twitter.com/jbrains/statuses/167297606698008576)
 
 # from my twitter
 * [MorganGeek](https://twitter.com/MorganGeek/statuses/420907517934178304) - Problem solving / Productivity : Good programmers write code after they found the solution. Un bon programmeur ne commence à coder qu'après avoir trouvé une solution.