Naturalism is motivated by the belief that the cause of evil in the sense of unnecessary suffering is belief in an imaginary supernatural realm. Epicurus is the classic exponent of this view. Gnosticism is motivated by the belief that the cause of evil and suffering is our imprisonment in the natural world, which was created by an inferior god.
But the body and the world are not prisons, joy is as real as suffering and redeems it, nature and supernature are both real, and the cause of evil and unnecessary suffering is mistaken philosophy/theology, such as Naturalism and Gnosticism, which are two sides of the same coin: the rejection of the Creator of this world.