In the 8th or the 9th century B.C., the Upanishads were composed out of the philosophic traditions that came from the earliest times of Indic civilisation. The thoughts contained in the Upanishads went on to form the basis of all major faiths in the subcontinent, in times to come.
This is a philosophy that sees a great oneness in all of creation. It is the same that is in each of us, in plants and trees, in animals, even in inanimate objects. All that there is, is perceived to be a part of the One. “Samsara”, the world of separated beings and objects around us, is believed to be an illusion we see owing to the limitations of our senses and sensibilities. (Four or five centuries later, the Greek philosopher Plato voiced similar thoughts about the illusory nature of what we perceive through our senses.)