“How can you prove that you have a Creator?”
Consequently, he (AS) responded: “I found myself not free from one of the two possibilities: either I have created myself, or someone else has created me. If I have created myself, then I am not free from one of two meanings: either I created myself while I was already existent, or I created myself while I was nonexistent. Hence, if I created myself, and I already existed, then I was self-sufficient of giving existence to myself. And if I was nonexistent, then you know that the nonexistent cannot bring about a thing. Therefore, the third meaning is proven that I have a Creator and that is Allah, the Lord of the Universe.”
Sheikh Saduq, Al-Tawhid, researched and corrected by Husseini, Hashem, p. 290, Qom, Islamic Publications Office, first edition, 1398 A.H.