The way I see it, we've evolved to see "white" things illuminated during the day as "white".
As they are illuminated both by the sun and the blue scattered light from the rest of the sky, the color we percieve as white is the color of the sun with some blue added, which is why the sun itself looks slightly yellow.
Had we evolved under a different star, or in an atmosphere with a different composition, I believe we'd have had an intensity curve experienced as white, but it would be very different from the one here.
Reductionist and proud of it.
Being ignorant is not so much a shame, as being unwilling to learn. Benjamin Franklin
Chase after the truth like all hell and you'll free yourself, even though you never touch its coat tails. Clarence Darrow
A person who won't read has no advantage over one who can't read. Mark Twain