the Upanishadic concept of Brahman-Atman identity claims

the Buddhist concept of anatta (no-self) claims

Anatta: No permanent, unchanging self exists

Nominalism

Nominalism claims only particular things exist, universals are just names

Kripke's Naming and Necessity showed

Kripke's Naming and Necessity showed identity statements like 'water is H₂O' are necessary a posteriori

Problem of universals

Universals question independent existence

Epiphenomenalism

Epiphenomenalism posits that consciousness is a by-product of physical brain states

Theory of forms

Plato's Theory of Forms posits abstract perfect Forms are more real than physical copies