In reading Chapter 2 in the Acts of the Apostles, “The Holy Spirit descended upon the apostles and they expressed themselves in foreign tongues.” My question is how could the apostles converse with each other if they were all speaking different languages? I know the people heard them speak in their own language when they started speaking, but afterward, could they speak in both languages or whenever they spoke did the people always hear them in their own language?
The NAB translation of the Bible says in Acts 2:4 that “All of them were filled with the Holy Spirit and began to speak in other languages as the Spirit gave them ability.” I would say that the classic Catholic interpretation of this passage would be that the author is describing the act of speaking in tongues here. In my experience, the gift of tongues (as described by St. Paul in 1 Cor. 12:4-10) most often comes in “angelic form” where a person utters sounds that would not be recognizable as any known human language on earth (random sounds to the neutral observer) but also, though less often, in the form of a foreign language that that person has no knowledge of. Both of these forms I have personally witnessed. St. Paul also describes the gift of interpretation of tongues. This involves someone else present who is given knowledge of the meaning of these random sounds. Someone may also be present, in the case of foreign language who speaks that language naturally and who can understand even what the speaker cannot. For example, I once witnessed a man speaking fluent German at a charismatic gathering, though he did not know German, and another person present, who was from Europe in the moment translated what he said. In the case of St. Peter giving his first homily where around 3000 came to believe in Christianity on that first Pentecost, we are told that many from different lands were able to understand what St. Peter was saying though they spoke a variety of languages (i.e. the reverse of the curse of confusion of languages at the Tower of Babel). That is an example of many present being given the ability to interpret tongues. In the other case your question describes, it is more likely that the gift of tongues being described was not uttered conversationally but more like the prophets of old, as they were overwhelmed and under the inspiration of the Holy Spirit speaking through them. My guess is that they were not actually conversing with one another in that moment but that, instead they were all given over to praising and thanking God in multiple languages spontaneously. In other words, this was a more spontaneous work of the Holy Spirit and not a case where God was miraculously and instantly teaching the Apostles foreign languages for their missionary work.