Theosis — from theos, God — is the aim of the Christian life in Eastern Orthodoxy: not merely moral improvement but the actual participation of the human person in divine life.
gregory-palamas distinguished God’s unknowable essence from God’s knowable energies — a distinction that made theosis philosophically coherent. One does not become God in essence (this would be blasphemy); one is transformed by participation in God’s uncreated energies (this is salvation).
Hesychasm — the inner discipline of the The Jesus Prayer and watchfulness — is the practical path of theosis. The claim, attested across centuries of Orthodox tradition, is that this path bears fruit in the real transformation of the person.
“God became man so that man might become God.” — Athanasius (paraphrased)