...The use of that last phrase, “style over substance” has always been, as Oscar Wilde observed, a marvellous and instant indicator of a fool. For those who perceive a separation between the two have either not lived, thought, read or experienced the world with any degree of insight, imagination or connective intelligence...
That's a great quote as it shows aesthetics are part of what the product is, rather than something you can "add later".
But most people's preconceptions are of design being primarily concerned with aesthetics and visuals. I find it helpful to show that there is another kind of design that deals primarily with functionality. You could label the two graphic design and interaction design. And of course both are interwoven and interdependent, but they often involve different skillsets and methods..
Stephen Fry