"In the history of thought, creative and critical epochs succeed each other. Periods of rich and glowing faith are followed by those of aridity and artificiality. When we pass from the Rig-Veda to the Yajur and the Sama-Vedas and the Brahmanas, we feel a change in the atmosphere. The freshness and simplicity of the former give place to the coldness and artificiality of the latter. The spirit of religion is in the background, while its forms assume great importance. The need for prayer books is felt. Liturgy is developed. The hymns are taken out of the Rig-Veda and arranged to suit sacrificial necessities. The priest becomes the lord... The religion of the Yajur-Veda is a mechanical sacerdotalism."