This quote by Epictetus suggests that for a person who values logic and reason, the only thing that is intolerable is irrationality. On the other hand, rationality, no matter how challenging or complex, is something they can endure or tolerate. This is because rational beings find comfort and understanding in logic and reason, even when it’s difficult or uncomfortable.

The irrational, however, is a source of frustration because it doesn’t follow the rules of logic or reason. It’s unpredictable, inconsistent, and doesn’t make sense. This can be highly frustrating for a rational being because they can’t understand it, predict it, or make sense of it. Therefore, it’s unendurable because it goes against their core values and understanding of the world.

In today’s world, this idea can be applied in many ways. For example, in the face of fake news and misinformation, a rational person would find it intolerable because it’s not based on facts or reason. They would rather endure the complex truth than accept irrational falsehoods.

In terms of personal development, this quote suggests that rational beings should focus on developing their understanding and application of reason and logic. This will not only help them endure the complexities and challenges of life, but also help them deal with the irrational elements of life. It’s about developing mental resilience and critical thinking skills to navigate a world that is often irrational and unpredictable.

In conclusion, Epictetus’ quote is a call for rationality and reason in a world that is often irrational and unpredictable. It’s a reminder that the path to endurance and resilience lies in our ability to understand, apply, and value reason and logic.