Horse outward similarity is an unreliable measure of relatedness. Besides the horse, there are six other species of genus "Equus" in the Equidae family. These are the ass or donkey, "Equus asinus"; the mountain zebra, "Equus zebra"; plains zebra, "Equus quagga"; Grévy's zebra, "Equus grevyi"; the kiang, "Equus kiang"; and the onager, "Equus hemionus". Horses can crossbreed with other members of their genus. The most common hybrid is the mule, a cross between a "jack" (male donkey) and a mare. A related hybrid, a hinny, is a cross between a stallion and a jenny (female donkey). Other hybrids include the zorse,
When a white horse is not a horse horse is not a horse, or a question if such a statement is possible, or both. Bryan W. Van Norden suggests that "the Advocate is only arguing that 'a white horse is not a horse' "could" be true, given a certain interpretation. He might acknowledge that, in another interpretation, 'a white horse "is" a horse.' " An alternative interpretation is offered in Feng Youlan's "History of Chinese Philosophy "(translated in 1952 by Derk Bodde): Strictly speaking, names or terms are divided into those that are abstract and those that are concrete. The abstract term denotes the universal, the concrete term