Eric has been seen as a foolish, immature young man in his interactions with other characters early in the play.
It is in Act 3 when Eric is questioned by Goole. He describes Eva as 'a good sport', making their brief relationship and the fact that she became pregnant seem a childish game. He does, however, offer her money, but Eva's scruples mean she will not take it. Despite being teh only one who even tries to help Eva, the other guests turn on Eric, even his father-
'You're the one I blame for this'
Once the inspector leaves after his profound speech, the older Birlings work to convince themselves that nothing happened, and the events surrounding the mysterious Eva Smith are not real and do not concern them. Eric, along with his sister Sheila, is horrified that the household has not absorbed the grim message communicated to them by the mysterious Inspector Goole.
Eric learns the most from the experience -
'It's what happened to the girl and what we all did to her that matters.'