diff --git a/PRINCIPLES.md b/PRINCIPLES.md
index c1f9d7a..7967db0 100644
--- a/PRINCIPLES.md
+++ b/PRINCIPLES.md
@@ -33,6 +33,7 @@
 * [Daniel Miessler](https://danielmiessler.com/projects/concepts/) - Lot of concepts summarized by Daniel Miessler
 * [Kent Beck](https://twitter.com/KentBeck/statuses/499584833929367552) - If you break a problem into sub-problems and the sub-problems aren't simpler than the original problem, git reset --hard and try again
 * [Stuart Sierra](https://twitter.com/stuartsierra/statuses/512009723282206722) - There's always a reason, no matter how strange the bug
+* [Johannes Seitz](https://twitter.com/Ookami86/statuses/515483645663252480) - Software Engineering best practice: Actually understand what you’re doing. Unfortunately it’s rarely used in practice.
 
 # 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.