Step 1: “Theism” is the belief in the existence of God or gods.
Step 2: “Atheism” is the lack of belief in the existence of God or gods, which directly aligns with the statement “God is nonexistent.”
Step 3: “Agnosticism” refers to the belief that the existence of God is unknown or unknowable, not necessarily nonexistent.
Step 4: “Reverence” refers to a deep respect, often towards a divine being, which does not fit the context of the sentence.
Thus, the correct answer is: “Atheism.”