The Six Systems of Sutras

There were other sutra-based philosophical movements outside the supposedly orthodox Hindu mainstream. Charvaka philosophy has its own foundational document in the shape of Prehāspati's Charvaka sutra. Each founding text is ascribed to a founding father, so that we have Gautama initiating Niyaya philosophy with his Niyaya sutra and Patanjali beginning Yoga philosophy with his Yoga sutra.