toKernel aim of making developer's life easier would not be met if debugging options had been left out.

All application events can be traced by defining the "log_debug" option as 1 in the application configuration file.

This option gives you a way to still get application debug information at runtime when its running in development mode, regardless of whether on screen display of errors has been enabled or not.

When developing a web aplication, you also have the option to receive debug information at the bootom of the web page.

For CLI, this debug information can be shown in the CLI output.