A mix. Product design is a balance of art and science. I am in
the Arizona product design profession and the first thing I do on
any new product design is to explore its basic form (what it looks
like). This is not a scientifically structured phase, rather it
relies on one's having a "good eye" for aesthetic. Once that's
finished, then the structured phase begins: defining geometry,
understanding the interfaces, applying appropriate materials, etc.
Ultimately product development is a back and forth iteration with
both structured and unstructured phases.