Design vs. Art?

Designers often struggle with the distinction between design and art. Perhaps one is instrumental and the other is not. Or design is for a client, and art is for oneself. I'm beginning to see the two more as points on a continuum. Early filmaker and theorist Dziga Vertov wrote that the possibility for film was "making the invisible visible, the unclear clear, the hidden manifest, the disguised overt, the acted non-acted; making falsehood into truth..." I think that this is the goal of both art and design, but that the emphasis is different for each. We could look at art and design along these lines:

art: making the invisible felt
design: making the invisible known

Of course, art and design strive towards each other in varying degrees. A landscape painting reveals a truth in a known as well as a felt manner. And a poster design reveals its topic in both an explicit and felt way. But I think it's fair to say that the emphasis in art is the felt, and the emphasis in design is the known.