Cosmos is a Greek word for the order of the universe. It is, in a way, the opposite of Chaos. It implies the deep interconnectedness of all things. It conveys awe for the intricate and subtle way in which the universe is put together.
But nirvana is a radical transformation of how it feels to be alive: it feels as if everything were myself, or as if everything---including "my" thoughts and actions---were happening of itself. There are still efforts, choices, and decisions, but not the sense that "I make them"; they arise of themselves in relation to circumstances. This is therefore to feel life, not as an encounter between subject and object, but as a polarized field where the contest of opposites has become the play of opposites.