tl;dr:Have you ever seen huge exception-handling blocks that throws an exception? Yiming shows an example and highlights the core problems: (1) It obscures the logic so unintended exceptions may be caught. (2) The code might end up catching different exceptions. (3) It rethrows a general exception, with the original exception ignored. This means that the root cause is lost - we don't know what exactly goes wrong. Yiming shows a better way to handle errors.