Final answer:
The persons who attempted to exorcise demons in the name of Jesus without being Christians are the seven sons of Sceva described in the Book of Acts. The prevalent belief in magic and spirits among early Christians and the blurring of lines by groups like the Gnostics provide context to why such incidents might occur.
Step-by-step explanation:
The individuals who attempted to cast out demons in the name of Jesus but were not really Christians are referred to in the New Testament, particularly in the Book of Acts. Although they are not named directly in the passages provided, a biblical narrative that references this topic is found in Acts 19:13-16.
It tells of the seven sons of Sceva, a Jewish chief priest, who tried to use the name of Jesus to perform exorcisms, even though they were not believers themselves. This act backfired when the evil spirit claimed to recognize Jesus and Paul (a true apostle), but not them, and they were overpowered by the man possessed by the demon.
The belief in magic and spirits was prevalent among early Christians and pagans alike. Christian leaders at the time regarded magic as dangerous and demonic, yet they, and their followers, still believed in the supernatural presence of magic and spirits in the world.
This overarching worldview could explain why some would use the name of Jesus for practices such as exorcism, despite not adhering to the Christian faith.
Various sects and interpretations within early Christianity, such as the Gnostics, also blurred the lines between religious practices and what was considered magical or superstitious at the time, which might pertain to the context of the question.