"If you have 2 strong points and 1 weaker one, your argument may actually be made weaker by adding the extra point. As Niro Sivanathan, an Associate Professor of Organisational Behaviour at London Business School, explains: Arguments don't add up. They average out.

"Next time you're making your case, consider sticking to your strong arguments."

Article: The Dilution Effect
Ted-Talk: The Counterintuitive Way to be More Persuasive