Scott Alexander uses three fictional stories to illustrate principles of non-empirical scientific reasoning, ultimately applying them to support the many-worlds interpretation of quantum mechanics. Longer summary

This post presents three fictional stories to illustrate important points about non-empirical arguments in science. The first story shows that even when two theories make identical predictions, it's important to choose the simpler one. The second story demonstrates that determining which theory is simpler isn't always straightforward and requires philosophical understanding. The third story ties these concepts to quantum mechanics, arguing that the many-worlds interpretation is preferable to single-world interpretations based on these principles. Shorter summary