We shall now examine two verses, which clarify two more terms for us, which we encounter in the Holy Bible. The terms "unbeliever" and "Idiotes" (Greek for private / lay person): 

"...If therefore the whole church comes together in one place, and all speak in tongues (λαλώσι γλώσσαις), and there come in those who are unlearned (Grk. "Idiotes", private/layperson), or unbelievers, will they not say that you are mad?   However, if all prophesy (προφητεύωσιν), and there comes in one who is an unbeliever, or one who is unlearned (Grk. "Idiotes", private/layperson), he will be checked by all, he will be questioned by all..."   [1 Corinthians 13:23, 24]

 "...because if you are blessing (officiating) in the spirit, how will the one who is in the place of the unlearned (Grk. "Idiotes", private/layperson) say 'Amen' upon your thanksgiving (Eucharist)? Because he will not know what you are saying..."  [1 Corinthians 14:16]

In the above verses, the "idiotes" (Greek for private / lay person) is differentiated from the "unbelievers" and from those who "speak in tongues" and those who "prophesy". Obviously, he would be the only faithful churchgoer with a problem, inasmuch as he would not understand what was going on around him. (Just like an infant that cannot participate in all of the events of his older brothers).  The "tongue-speaking sons" in this instance do not seem to have any problem with what was going on around them - even though they did not have the gift of "interpretation" or "prophecy".

In church, the "idiotes" (Greek for private / lay person) who does not speak in tongues is the "infant" among the faithful and in the category of "servant", who could only say "Amen" during the Service.  The "idiotes" (Greek for private / lay person) was not an "unbeliever", therefore he was a believer.  The "idiotes" (Greek for private / lay person)  was still struggling to be cleansed.

So far, we have observed that: In a Christian congregation during the time of the Apostles, the following groups existed:  1. The unbelievers, 2. The "idiotes" (Greek for private / lay person), aka "infants", or "those undergoing cleansing", or "servants", 3. The sons, or "those who spoke in tongues in the spirit", who could have: a. the gift of Interpretation b. the gift of Prophecy, or other gifts, that we have not preoccupied ourselves with.