The Meaningful Life Argument, that if God were to exist life would lose meaning

A perennial topic in the philosophy of religion is the existential question of whether God exists. Arguments in support of theism include the ontological, cosmological, teleological, and moral arguments

The most promising argument in support of anti-theism is the Meaningful Life Argument, which suggests that God’s existence would make certain individuals’ lives worse, for those individuals have life plans so intimately connected with God’s non-existence that, if it turned out God exists, their lives would lose meaning if God were to exist. 

for instance, it seems perfectly consistent for an atheist who denies that God exists to simultaneously believe that God’s existence would be good,
 It also seems consistent for a theist who is convinced that God exists to hold that there are negative consequences of God’s existence