Matt Gemmell, in a piece about superfluous design in iPhone apps, presents a great philosophy:
There’s a question I try to ask myself when I’m creating something: “Is this true?”
I define truth here not as factual accuracy, but as fidelity to both intent and embodiment. A design is true if it fulfills its requirements judiciously, and yet surprises and delights its intended audience. An app is true if it has a purity of vision and focus, and serves its intended customers on their terms. A piece of writing is true if it resonates with the people who read it – even if the details must be changed in order to better do that.
Truth, in this sense, is the opposite of betrayal, or carelessness. It’s the antithesis of compromise, for any reason except making something as good as possible.
Finding this truth is the crux of design. Truth isn’t an ideology that you need to understand so you have a basis for implementation. It is represented by how the design satisfies the ideology in practice. Truth isn’t a concept but the marriage of the concept and its execution.
When you create, seek to design and produce truth. If the scope of your work is too large, matching it will be difficult; too simple and your design may overachieve. Be comfortable with the cycle of adjusting the concept and the implementation until you find them in harmony. In this harmony is truth.