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 When a white horse is not a horse When A White Horse Is Not A Horse (), also known as the White Horse Dialogue (), is a famous paradox in Chinese philosophy. Gongsun Long wrote this circa 300 BC dialectic analysis of the question 'Is "white horse not horse" permissibly assertible?'. The White Horse Dialogue ("Baima Lun") constitutes chapter 2 of the eponymous "Gongsun Longzi" "Master Gongsun Long", who was counted among the "School of Names" (aka "Logicians" or "Dialecticians") in the Hundred Schools of Thought. Most of Gongsun's writings have been lost and the received "Gongsun Longzi" text only