Do demons exist? If so, what are they? Our Gemara here mentions them in a variety of scenarios that show them to be living creatures, who live and die, need space and otherwise share the earth with the rest of humanity.

It is well-known that the Rambam did not believe in demons, see for example commentary on the Mishna (Avoda Zara 4:7) where he lists belief in demons amongst the defective and degenerate ideas that come from idolatry. Whenever a halakhic Gemara references a demon, the Rambam would follow the halakha but use a more naturalistic explanation for the phenomenon. For example, the Gemara (Gittin 66a) has concern that a disembodied voice from a pit directing people to write a get (divorcement bill) in his name might be a demon. The Rambam (Laws of Divorce 2:13) records the halakhic concern not as a demon per se, but as making sure that there is positive identity. Or for example, Gemara Berachos (3a) discusses different possible dangers coming from entering an abandoned building including the presence of demons, while Rambam (Laws of Murderers and Preservation of Life 12:6) merely notes it as “dangerous”. Or compare Gemara (Avoda Zara 12b) and Rashi’s concern about drinking water under certain night time conditions due to the demon “shavriri”, while Rambam (Laws of Murderers and Preservation of Life 11:6) notes the same concern but lists natural dangers such as leeches or snake venom in the water.

Obviously, the Rambam did not disagree with the Gemara. Rather, he assumed the rabbis used the prevailing superstitions of the masses in order to promote healthy practices. This has precedent in the Gemara where the Am Haaretz’s superstitious avoidance of impurity above other sins allowed the rabbis to protect children from molestation. They declared that gentiles had the severe impurity of zav, though in fact the real concern was that Jewish children would play with their gentile neighbors who were promiscuous and end up being molested. See Gemara Shabbos (17b). 

Think of it, imagine trying to teach a primitive person about germs and telling them that they need to wash their hands. They don’t see germs because they are invisible. But if you tell the primitive that there are demons that need to be washed away he may follow that. In fact, one can offer a good argument that the true reason for washing hands before bread was in order to promote sanitary practice, even though the most popular stated reason was to preserve a custom regarding ritual purity. See Mishna Berura 158:1 where both reasons of purity and sanitary conditions are offered for the ritual requirement of washing hands.  When you look into this particular custom and reason, from a ritualry perspective it seems far fetched:  The Cohanim were required to wash their hands before eating Terumah because their hands were declared rabbinically impure.  Then, on top of that rabbinic prohibition, all Jews, not just Cohanim, were required to wash their hands so as not to forget the custom in non-Temple times.  So, we are forever required to wash our hands in order to preserve a custom amongst the priests, which was in the first place, only rabbinic?  It seems far fetched.  However, one of the concerns was cleanliness it may be easier to understand that the rabbos employed the “boogeyman” of impurity to motivate the masses to maintain cleanliness.  While I doubt the rabbis understood germs in the Louis Pasteur sense of the word, I am confident that their tradition, mesorah, and Ruach HaKodesh allowed them to sense the danger of germs, more or less.

Another point I would like to make is that it is easy to be arrogant, and claim that we modern people are scientifically sophisticated and do not believe in demons. I think that is simplistic. We all have, “demons“. That is, the world is far more complicated and intertwined than we can understand. We do sense that there are forces that work against us beyond our control. One of the great spiritual psychoanalysts, Carl Jung, made some powerful observations about modern life and ancient demons which I will quote:

“Contemporary man is blind to the fact that, with all his rationality and efficiency, he is possessed by "powers" that are beyond his control. His gods and demons have not disappeared at all; they have merely got new names. They keep him on the run with restlessness, vague apprehensions, psychological complications, an insatiable need for pills, alcohol, tobacco, food - and, above all, a large array of neuroses”

Man and his symbols” by C.G. Jung

In the mythology of earlier times, these forces were called mana, or spirits, demons, and gods. They are as active today as ever. If they go against us, then we say that it is just bad luck, or that certain people are against us. The one thing we refuse to admit is that we are dependent upon “powers” that are beyond our control.

Carl Jung; Man and His Symbols