FranciscoPope Francis returned to one of his favorite topics Friday morning, telling his hearers that the devil seeks above all to become master of their consciences, so they no longer can tell right from wrong.

The Gospel reading at Mass spoke of Jesus casting out devils, and the Pharisees accusing him of driving out demons by the power of the Beelzebul, the prince of demons. It also spoke of a devil returning after being cast out, bringing other demons with it and setting up shop in the house where it had been before.

In his homily in the chapel at the Saint Martha residence, the Pope said that in the spiritual life “temptations always return, the evil spirit never gets tired.” If he has been kicked out once, he is patient, waiting to return, and “If you let him in, you fall into a worse situation.”

In fact, Francis said, in the gospel story, at first it was clear that it was the devil who was causing problems. But afterward, “The evil one conceals himself, and comes with his very polite friends, knocking at the door, asking permission, but then moves in and spends time with the man and, little by little, starts giving the orders.”

With his “good manners,” Francis said, the devil makes the man fall into moral relativism, calming his conscience.

We start saying things like “This happens everywhere” and “We are all sinners,” Francis said. Yet “When we say everybody, we mean nobody,” he said. “And so we live this worldliness that is the child of the evil spirit.”

“Calming the conscience, numbing the conscience, this is a great evil,” he said.

“When the devil manages to numb your conscience he has won a real victory,” Francis said, because “he has become the master of your conscience.”

The Pope said that the key to combatting the devil is discernment and vigilance. We need to be able to discern situations, he said, to see what comes from God and what comes from the devil who “always tries to deceive” and to “make us choose the wrong path.”

The Christian cannot just accept anything, but must “discern and look well to see where things come from, and what their root is,” he said.

Francis said that the Church “always encourages us to examine our conscience: What happened in my heart today, why? Did this well-mannered devil visit me today with his friends?”

“Where do these comments, these words, these teachings come from, who says this? Discern and keep watch, so as not to let in the one who deceives, seduces and fascinates,” he said.

“We ask the Lord for this grace,” he said.