Keeping the internals of code simple is at the heart of what it means to think like a programmer, especially a Unix programmer. But keeping interfaces simple demands the opposite discipline — learning how not to think like a programmer, and instead thinking like the end-users that you are serving. Interfaces that are really smart match the needs of those users.

Identifying with the end-user is a difficult and humbling task for many programmers. But if you nerve yourself to the effort, you may find great satisfaction in writing programs which are as responsive and intuitive from the outside as they are elegant within. The ultimate test of software (as with any other tool) is how well it serves human beings, and it is in serving other human beings that we reach the true zenith of craftsmanship.

If that's too abstract and idealistic for you, think of this. No matter how skilled you are, there are many times when you will be the end user. When you give yourself standing to demand good UI design from others by setting an example of good UI design yourself, the time and sanity you save will ultimately be your own. At the zenith of craftsmanship, through serving others you serve yourself — and vice-versa.

To reach that zenith, go back to zero. In [TAOUP] we used some ancient ideas from Zen Buddhism to illuminate the craft of writing code. Here is one that applies to user-interface design: beginner's mind. “Beginner's mind” is the stance that approaches a task with no assumptions, no habits, perfect ignorance awaiting experience. Achieving beginner's mind involves forgetting what you know, so that you can learn beyond the limits of what you know.

To design interfaces for end-users — to keep them simple, stupid — approach the interface-design task with beginner's mind.