Kung-sun Lung was a dialectician who lived at the time of the Six Kingdoms. He wrote a treatise on “Hard and White” and, to illustrate his theory, said that a white horse is not a horse. To show that a white horse is not a horse, he said that “white » is that by which one names the color and horse that by which one names the form. The color is not the form, and the form is not the color. 
Huan T’an_Pokora  “New Treatise”. Fragment 135A, p. 124.

This kind of argument is all the fashion these days:

There are now people who doubt everything. They say that the oyster is not a bivalve, that two time five is not ten.
Huan T’an_Pokora  “New Treatise”, p. 1

But it doesn’t even deserve a rebuttal:

Kung-sun Lung often argued that “a white horse is not a horse”. People could not agree with this. Later, when riding a white horse, he wished to pass through the frontier pass without a warrant or a passport. But the frontier official would not accept his explanations, for it is hard for empty words to defeat reality.
Huan T’an_Pokora  “New Treatise”. Fragment 135B, p. 124.
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Pokora Timoteus, 1975 Sin-Lun (“New Treatise”) and Other Writings by Huan T’an (43 B.C. – 28 A.D.). An Annotated Translation with Index. Ann Arbor Center for Chinese Studies The University of Michigan. P. 124