The Essence of the Aitareya and Taittiriya Upanishads
Chapter 5: Ananda Mimamsa
We will continue the subject of the Taittiriya Upanishad. We observed that our individuality is constituted of different layers, and these layers are called koshas in Sanskrit. There are primarily five such koshas, or sheaths, in which our consciousness is enveloped. These sheaths are nothing but the forces of objectivity that pull the consciousness outwardly in terms of space and time. Thus it becomes clear that these sheaths are not substances or material objects like five walls that may be built round a person sitting inside a room. They are mere urges of consciousness to move outward in greater and greater density, and with more and more of impetuosity towards externality of experience.