Which for a while believe (oi pro kairon pisteuousin). Ostensibly they are sincere and have made a real start in the life of faith. They fall away (apistantai). Present middle indicative. They stand off, lose interest, stop coming to church, drop out of sight. It is positively amazing the number of new church members who "stumble" as Mark 4:17 has it (skandalizontai), do not like the pastor, take offence at something said or done by somebody, object to the appeals for money, feel slighted. The "season of trial" becomes a "season of temptation" (en kairwi peirasmou) for these superficial, emotional people who have to be periodically rounded up if kept within the fold.