Now days with modern science it seems that anyone who has belief in demons is considered a fool; yet it’s not that simple…
Many Kabbalistic texts, Torah, Mishna, Talmud are full of description around demons and their powers, yet we don’t see any proof to their existence. How come?
Kabbalists teach us that Creator in His infinite wisdom created two systems – System of Kedusha (holiness/desire to bestow) and System of Tumah (impurities, desire to receive for the sake of receiving) as it’s explained in depth by Baal HaSulam. These two systems were created to give us – the creation – freedom of choice. A lot is already written on this topic, so I won’t go further into this.
For these two systems to co-exist in harmony and provide us with true freedom of choice there must be balance – i.e. the forces must be equal in power. Therefore when Sanhedrin requested from the Creator to take away from us the nisanyon (test) of idolatry we immediately lost the ability to prophesy in the same moment as idolatry was taken away from us.
Thus in our time we can’t even comprehend how one would be servering a stone – yet our ancestors were far from fools – they had tangible benefits from serving idols and the closet desire that we could somehow compare their hunger to work the idols can be only compared to our nowadays sexual desires for intimacy (but even that is far from what they felt).
Thus, just as prophesy was taken away from us once we asked to be absolved from idolatry so the power of demons diminished once our level of Kedusha started to decline. Ben Ish Chai – widely accepted Kabbalist – wrote about this in several of his commentaries. I also would like to share a link that can give an insight to how our ancestors were able to interact with demons when their level allowed it