# Cognitive complexity The more difficult an explanation is to understand, the less appealing it is and the more effort it requires to evaluate. Cognitive complexity is a tax that needs to be paid every single time. There's no way around it. A complex software project is hard and costly to maintain because it takes a lot of effort to construct the mental context necessary to be able to work on it. A complex business offering negatively affects buying decisions. If prospects need to make too much effort to evaluate an offer, they'll generally back away from the deal. That's why it's critical to focus on simplicity. Simplicity and correctness win hands down.