This question already has an answer here:

Catholics, and to my understanding other Trinitarian Christians, believe and teach what is borne by scripture [cf. Eph 4:4-5] i.e. there One God the Father, One God the Son, and one God the Holy Spirit.

The Father, being the Origin without origin is perhaps easier to grasp.

Why can't his Son have his own son and so on ad infinitum and therefore be a corresponding infinite number of spirits?

According to Catholic theology, why are there two and only two processions in the Godhead and therefore three and only three persons in one God?

marked as duplicate by curiousdannii, 3961, Matt Gutting, BYE, user13992 Jan 29 '15 at 18:59

This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.

  • I think your logic is backwards... there are three persons and therefore two processions. – curiousdannii Jan 29 '15 at 0:18
  • @curiousdannii Agreed, especially in light of Peter Turner's answer. – Matt Gutting Jan 29 '15 at 3:56
  • I recommend a review of this answer from Geremia: christianity.stackexchange.com/a/28414/10486 – bruised reed Jan 29 '15 at 8:07
  • @curiousdannii My understanding, in a human way of thinking, is that it's the processions that give rise to the persons. – user13992 Jan 29 '15 at 20:25