There is much demonization in the world today. The devil is prevailing because contemporary individuals have granted him numerous rights and are subjected to terrifying demonic influences. It has been aptly said: ‘Once the devil used to deal with people, but not anymore! He simply sets them on their way and says, ‘Have a good journey!’ and people continue on their path.’ This is alarming! You see, in the land of the Gadarenes, the demons requested permission from Christ to enter the swine. This occurred because the swine did not give the devil the right to enter them. Christ allowed them to enter as a means of punishing the Israelites, who were prohibited from consuming pork.”
-Father, there are some who say that the devil does not exist.
-Yes, someone once told me, “Remove from the French translation of the book of Saint Arsenios of Cappadocia those parts that refer to the possessed, because Europeans won’t understand them. They don’t believe that the devil exists.” You see, they explain everything through psychology. If those demon-possessed individuals from the Gospel had gone to psychiatrists, they would have been subjected to electric shocks. Christ took away the devil’s power to do harm. Only if a person grants him the power, can he do harm. When someone has no connection to the Sacraments of the Church, they give rights to the tempter and receive demonic influence.
-Father, how else can someone grant him rights?
– Logic, speaking against, envy, self-will, disobedience, and insolence are the characteristics of the devil. According to the extent to which a person possesses these, they also receive external influence… However, when the soul becomes purified, the Holy Spirit will dwell within the person and fill them with Grace. But if the soul becomes stained with mortal sins, the unclean spirit will dwell within them. And when the soul is not stained with mortal sins, it is only under the influence of the cunning spirit.
In our era, unfortunately, people do not want to cut off their passions or their own will, and they do not accept advice. Besides this, they also speak with insolence, thus driving away the Grace of God. And after this, wherever the person may be, they cannot grow, as they receive demonic influences. They are outside of themselves because the devil commands them from the outside. It is not openly within them — God forbid! — but even from the outside, the devil can give commands. When a person is forsaken by Grace, they become worse than the devil
Indeed, there are certain things that the devil does not do himself but rather tempts people to do. For example, he does not commit crimes himself but rather tempts humans to commit them. And in this way, people become demonized. See Luke 8:26-33.  Here, the Elder refers to the rationalistic mindset that arrogantly opposes the spiritual one.
Excerpt from With Pain and Love for Contemporary Man – Saint Paisios the Athonite, Evanghelismos Publishing.