The Kaushitaki Upanishad (, ) is an ancient Sanskrit text contained inside the Rigveda. It is associated with the Kaushitaki shakha, but a Sāmānya Upanishad, meaning that it is "common" to all schools of Vedanta. It was included in Robert Hume's list of 13 Principal Upanishads, and lists as number 25 in the Muktika canon of 108 Upanishads. The Kaushitaki Upanishad, also known as Kaushitaki Brahmana Upanishad, is part of the Kaushitaki Aranyaka or the Shankhayana Aranyaka. The Kausitaki Aranyaka comprises 15 chapters and four of these chapters form the Kaushitaki Upanishad. Chronology The chronology of Kaushitaki Upanishad, like other Upanishads, is unclear. It is based on an analysis of archaism, style and repetitions across texts, driven by assumptions about likely evolution of ideas, and on presumptions about which philosophy might have influenced which other Indian philosophies. Kaushitaki Upanishad was probably composed before the middle of the 1st millennium BCE. Ranade places Kaushitaki chronological composition in the third group of ancient Upanishads, composed about the time of Aitareya and Taittiriya Upanishads. Juan Mascaró posits that Kaushitaki Upanishad was probably composed after Brihadaranyaka, Chandogya and Taittiriya Upanishads, but before all other ancient Principal Upanishads of Hinduism. Deussen as well as Winternitz consider the Kaushitaki Upanishad as amongst the most ancient prose style Upanishads, and pre-Buddhist, pre-Jaina literature. Ian Whicher dates Kaushitaki Upanishad to about 800 BCE. According to a 1998 review by Patrick Olivelle, and other scholars, the Kaushitaki Upanishad was likely composed in a pre-Buddhist period, but after the more ancient Brihadaranyaka and Chandogya Upanishads, placing the Kaushitaki text between 6th to 5th century BCE. Structure The Kaushitaki Upanishad is part of the Rig veda, but it occupies different chapter numbers in the Veda manuscripts discovered in different parts of India. Three sequences are most common: the Upanishad is chapters 1, 2, 3 and 4 of Kausitaki Aranyaka, or 6, 7, 8, 9 chapters of that Aranyaka, or chapters 1, 7, 8 and 9 in some manuscripts. Paul Deussen suggests that these different chapter numbers may reflect that Upanishadic layer of Vedic literature were created and incorporated as spiritual knowledge in the pre-existing Aranyaka-layer of Vedic texts, and when this was being done in distant parts of India, the sequencing information was not implemented uniformly. The Kausitaki Upanishad is a prose text, divided into four chapters, containing 6, 15, 9 and 20 verses respectively. There is some evidence that the