I believe most in educated intuition, in what you get through profound experience.
I believe one should design for the advantage of the largest mass of people, first and always. That takes care of ideologies and sociologies.
Ugliness does not sell.
The most beautiful curve is a rising sales graph.
Industrial design keeps the customer happy, his client in the black and the designer busy.
It's a simple exercise; a little logic, a little taste, and the will to cooperate.