Justin Martyr, Irenaeus, and Tertullian testify regarding exorcism in the early church in the pre-Christian Ancient Roman Empire 1,800 years ago

The reality of of demon possession to the early Church

Painting of Saint Francis Borgia performing an exorcism, by Goya

The early Church considered demon possession a dangerous reality.  They dealt with it consistently and effectively, and their efforts remain for posterity.

Justin Martyr (c. 150 AD)

Saint Justin Martyr

Justin Martyr (c. 150 AD) said in his Dialogue with Trypho, a Jew: "For we call Him (Jesus) Helper and Redeemer, the power of whose name even the demons do fear and at this day, when they are exorcised in the name of Jesus Christ, crucified under Pontius Pilate, governor of Judaea, they are overcome."

Irenaeus (c. 190 AD) 

An engraving of St Irenaeus, Bishop of Lugdunum in Gaul (now Lyons, France)

Irenaeus (c. 190 AD) recorded this concerning Christians: "For some do certainly and truly drive out devils, so that those who have thus been cleansed from evil spirits frequently both believe [in Christ], and join themselves to the Church."

Tertullian (c. 200 AD) 

A woodcut illustration depicting Tertullian

Tertullian (c. 200 AD) discussed the well-known conflict of Christians and demons with Scapula, proconsul of Africa.  "As for daemons, we not only abhor them, but we overcome and draw them forth daily, and we drive them out of men, as is known unto very many of yourselves."

Demon worship

Saint Wolfgang and the Devil, by Michael Pacher.

Demon worship was rampant in the ancient word, the wealth of deities available for adoration in the Greco-Roman sphere, mind-boggling.  In addition to the official Roman pantheon of gods and goddesses, there were divine infiltrators from any number of cultures, conquered under the rule of Rome.  The Church answered the threat of these religions by calling them what they were: the organized worship of demons.

Mithras

Bas-relief of the tauroctony of the Mithraic mysteries, Metz, France.

One example of this is Justin Martyr's criticism of the cult of Mithras, whose secret rites included the perversion of the Christian Last Supper:

For the apostles, in the memoirs composed by them, which are called Gospels, have thus delivered unto us what was enjoined upon them; that Jesus took bread, and when He had given thanks, said, "This do ye in remembrance of Me, this is My body'" and that, after the same manner, having taken the cup and given thanks, He said, "This is is My blood;" and gave it to them alone.  Which the wicked devils have imitated in the mysteries of Mithras, commanding the same thing to be done.  For, that bread and a cup of water are placed with certain incantations in the mystic rites of one who is being initiated, you either know or can learn.

History reveals a widespread belief in supernatural powers and supernatural beings.  It details real and constant battles against the forces of darkness, battles that resulted in consistent victories.

Source: Martin, Walter, Jill Martin Rische, and Kurt Van Gorden. The Kingdom of the Occult. Nashville, TN: Thomas Nelson, 2008, pages 524-525.