Critical Thinking Via 5 Whys and First Principles

Early in my career, my departmental VP hired a well-known management consulting firm to diagnose why an important project had failed. The management consultants used a technique called “5 Whys” to get past discussions of the failed outcomes and try to unearth the root causes. As the name implies, the technique is based on asking Why five times in a row – with the assumption that by the last Why you’ll reach the true cause of a problem.

This technique can work well (here’s a real-world example from a kitchen range manufacturer) but has its limitations. In a complex situation, you can suffer from tunnel vision which might lead to an incorrect conclusion. To counteract this, there are variants of the 5 Whys technique which intentionally create branches (alternative theories) and therefore explore new ground. In mathematics this is called avoiding a local maximum to search for a global maximum. For those interested in learning more, here’s a good article on variants of the 5 Whys technique.

The recent Elon Musk-fueled craze around first principle thinking reminded me that everything old is new again. First principle thinking, for those who haven’t seen the endless articles trumpeting this breakthrough, is a mode of thinking “designed to relentlessly pursue the foundations of any given problem from fundamental truths.” In science, theoretical work is considered to be from first principles if it starts directly with established science and doesn’t rely on assumptions. This approach isn’t really new: A case can be made it originated more than 2000 years ago with Aristotle.

Confused? Here’s a frequently-referenced video of Elon describing how first principles thinking challenged the traditional economics of making batteries:

5 Whys and First Principles are both examples of critical thinking but differ in how they approach the problem. 5 Whys is top down; starting with the observed result and trying to discover the underlying cause. On the other hand, the First Principles approach builds from basic truths to discover new solutions. Each has merit and is appropriate in different circumstances. When in doubt, try them both.

Regardless of which approach you use, the key to critical thinking is to be sensitive to your built-in biases and learn to challenge surface explanations. Be sure to ask more questions; just remember it’s hard to ask good questions.