It is necessary, if we wish to understand the principles of Hindu medicine, to glance at the philosophy and religion of the Brahmans and Buddhists. The Aryan conquerors descending through the Himalayas were a sober, industrious, courageous people, who lived a pastoral life, and knowing nothing of the enervating attractions of great cities, required no other medical treatment than simple folk medicine everywhere affords. Their earliest literature is found in the “Vedic Hymns,” the “Sacred Books of the Hindus,” which were composed by the wisest and best of the men, who were warriors and husbandmen, and the priests and physicians of their own households. They gradually acquired priestly supremacy over a wider range. Thus arose the Brahmans, the “Offerers of Potent Prayer.” The _Rig-Veda_ refers to physicians, and speaks of the healing power of medicinal herbs; and the _Atharva-Veda_ contains an invocation against the fever-demon, so that medical matters began very early to receive attention after the conquest of India by the Aryans. “Hinduism,” says Professor Monier Williams, “is a creed which may be expressed by the two words, spiritual pantheism.”[225] Of all beliefs this is the simplest. Nothing really exists but the One Universal Spirit; man’s soul is identical with that Spirit. Separate existence apart from the Supreme is mere illusion; consequently every man’s highest aim should be to get rid for ever of doing, having, and being, and strive to consider himself a part of the One Spirit. This in a few words is esoteric Hinduism. When we attempt to study the endless ramifications of the exoteric, or popular belief, the system, so far from being simple, is infinitely complicated. God may amuse Himself by illusory appearances. Light in the rainbow is one, but it manifests itself variously. All material objects, and the gods, demons, good and evil spirits, men, and animals are emanations from the One Universal Spirit; though temporarily they exist apart from him, they will all ultimately be reabsorbed into their source. In the Sanskrit language, which is the repository of _Veda_, or “knowledge,” we have the vehicle of Hindu philosophy. The systems of Hindu philosophy which grew out of the third division of the _Vedas_, called the _Upanishads_, are six, and are given in Professor Monier Williams’ work already referred to as— 1. The Nyāya, founded by Gotama. 2. The Vais’eshika, by Kanāda. 3. The Sānkhya, by Kapila. 4. The Yoga, by Pantanjali. 5. The Mīmānsā, by Jaimini. 6. The Vedānta, by Bādarāyana or Vyāsa. We know neither the dates of these systems, nor which of them preceded the other.