What alternative does the skeptical atheist, such as Bertrand Russell offer in response to the Christian mystic? He agrees with the mystics that without God, life is meaningless, but seeing that there is no evidence for any supernatural realm, he therefore rejects meaning. He agrees with the mystics that without God man has no free will, so he rejects free will and volition. He agrees with the mystics that without God, there can be no morality ("If God is dead, all is permitted" as that quote falsely attributed to Dostoevsky goes) so he rejects morality. In the crucial question of man's existence, the skeptic and the mystic agree that man has no purpose, volition, or virtue apart for some external entity. Man's life in itself therefore, is meaningless, the skeptics and the mystic agree, and only has value so far as man offers himself as a sacrifice to some greater entity or purpose.
The skeptic denies the supernatural, but he usually proposes some other "higher" purpose for existence. He replaces subservience to the supernatural with subservience to some other, equally mystical or collectivist entity, such as service to society (socialism), the state (communism), the race (fascism), the environment (environmentalism), the ethnic group (multiculturalism) or emotionalism (Nietzschean nihilism). The skeptic simply replaces the worship of one supernatural and unknowable entity with another. The mystics present man as a pathetic ghost, unworthy of life, in conflict with his physical (baser) nature, and existing only as a sacrificial offering for another realm, The skeptics present man as a Frankenstein - a walking bag of chemicals without freedom, meaning, or self-esteem. The mystics demand that man sacrifice his worldly values for the supernatural, and the skeptics either argue that man sacrifice his life to the collective, or argue that he should pursue whatever values he wants, while denying his basic means (his rational mind) of achieving it.