The fifth brahmana of the second chapter introduces the "Madhu theory", thus giving this section of the Upanishad the ancient name "Madhu Khanda". The "Madhu theory" is one of the foundational principles of Vedanta schools of Hinduism, as well as other āstika schools of Indian philosophies. "Madhu" literally means "honey", or the composite fruit of numerous actions on the field of flowers. In the "Madhu theory", notes Paul Deussen, the Brihadaranyaka Upanishad asserts that "Atman exists" (soul exists), that all organic beings (plants, animals, human beings and gods) are wandering souls yet One with each other and the Brahman (Cosmic Soul); it further asserts that inorganic nature (fire, air, earth, water, space) is the field where the beings act, and where their numerous actions create fruits that they separately and together experience. The Upanishad then states that everything is connected, beings affect each other, organic beings affect the inorganic nature, inorganic nature affects the organic beings, one is the "honey" (result, fruit, food) of the other, everyone and everything is mutually dependent, nourishing and nurturing each other, all because it came from one Brahman, because it is all one Brahman, because all existence is blissful oneness. This theory appears in various early and middle Upanishads, and parallels Immanuel Kant's doctrine of "the affinity of phenomena" built on "the synthetic unity of apperception".