What Did Church Membership Classes Look Like in the First Century?

Churches generally offer membership classes or even classes for new believers. In most cases, these classes teach the basics of the faith or what someone should know before joining a church.  These kinds of classes are not new. Early Christians called such training catechesis. In the early years, Christians taught the basics of life and doctrine through catechetical instruction. This kind of training seems to have started very early in church history, even during the apostolic age. So it is worth asking the questions: what did the apostolic church teach new believers? What were the fundamentals of the faith? What...