KISS Principle (Occam's Razor)
The principle that simpler explanations are preferable to complex ones, and that unnecessary concepts should be shaved away. It is a heuristic for theory selection and problem-solving.
THE IDEA
15. KISS and Tell
We consider it a good principle to explain the phenomena by the simplest hypothesis possible. —Claudius Ptolemy
It is futile to do with more things that which can be done with fewer. —William of Occam
To the same natural effects we must, so far as possible, assign the same causes. —Isaac Newton
Whenever possible, substitute constructions out of known entities for inferences to unknown entities. —Bertrand Russell
KISS
Occam's razor: theories must be succinct—unnecessary concepts have to be shaved away. In the scientific arena, the simplest theory capable of explaining the evidence wins. We abandon a simple theory only when there’s a more complicated theory that explains more evidence than the simple theory.
KISS—Keep It Simple, Stupid—is a good motto for lots of things. Complicated theories and proposals and plans are likely to cause foul-ups. In my experience, people who sacrifice comprehensiveness and complexity for simplicity are more likely to come up with answers—to something at least, if not to the original question.
Reductionism
A reductionist explanation holds that some seemingly complex phenomenon or system is nothing more than the sum of its parts. The principle of parsimony requires us to explain phenomena at the simplest level possible and to add complications only as they become necessary.
Know Your Own Strength
We don’t recognize how easy it is to generate hypotheses about the world. This is one type of confirmation bias. Scientists make all of these mistakes: sometimes generate hypotheses too readily, fail to recognize how easy it is to explain away contrary evidence, and not search for procedures that could falsify their hypotheses.
Falsifiability
If someone makes a theoretical claim but can’t tell us what kind of evidence would count against it, we should be especially wary of that person’s claim. The falsifiability principle is now enshrined in law in several states as a criterion for teaching something purporting to be science.
Popper and Poppycock
Karl Popper promulgated the view that science proceeds solely by conjecture and falsification. Though correct, Popper’s contention is pragmatically useless. Science advances mostly via induction from facts that support a theory.
The Hocs: Ad and Post
Ad hoc postulates are amendments to a theory that don’t follow directly from the theory and serve no purpose other than to keep the theory propped up. Post hoc explanations are contrivances after the data are in to explain what was not predicted in advance.
Summing Up
Explanations should be kept simple. They should call on as few concepts as possible, defined as simply as possible. Effects that are the same should be explained by the same cause. Reductionism in the service of simplicity is a virtue; reductionism for its own sake can be a vice.
When to use it
When developing a new product, start with the simplest version that can be tested and gather feedback quickly.
In medical diagnosis, consider the most common and simplest explanations first (horses, not zebras).
When constructing a scientific theory, prefer the hypothesis that makes the fewest assumptions.
FROM THEORY TO EVERYDAY LIFE
In practice
Ptolemy's epicycles
Ptolemy used multiple epicycles (circles on circles) to explain the movement of Mars, fitting data perfectly but being overly complex compared to a heliocentric model. An overcomplicated theory can achieve even a perfect fit.
Obese eating behavior study
A simple hypothesis that obese people defend a higher set point for weight explained much eating behavior, despite not covering all facts. This simple theory led to progress while more complicated alternatives did not.
A MOMENT TO REFLECT
Put it to work.
Think of a time when you or someone else proposed a complex explanation for a simple event. Could a simpler explanation have sufficed?
How might the KISS principle apply to evaluating business strategies or scientific hypotheses?
What evidence would you need to confidently reject a cherished theory, and how could you test it?
Often confused with
CONTINUE THE CONVERSATION
Source texts
- Mindware Tools for Smart Thinking (Richard E. Nisbett)