Shalom and thank you for your question! Please accept my apologies that my answer was delayed due to various pressures. You wish to know if ghosts exist? Firstly, there are sources that say that in the Holy Land of Israel, ghosts either do not exist, or are very rare. In other places however, according to sources, the presence of ghosts is indeed a possibility.
Ghosts and evil spirits are only messengers of G-d and can do neither good nor evil on their own accord. There is a story – quite a spooky one – that occurred during the lifetime of a certain righteous Jew a few hundred years ago who was well-versed in the esoteric aspect of Torah – the inner dimension.
Very briefly, the story is that in a certain town in Eastern Europe, lived a childless Jewish couple. They were very generous and gave a lot of charity and helped people – BUT – they had a terrible habit of cursing and using foul language. After their death, people soon became afraid to go near the house the couple had occupied, because it had been overtaken by evil spirits. These spirits took on ghastly forms like half chicken and half dog or other horrible concoctions, and made sickening noises, frightening the wits out of anyone who had the misfortune to be in their proximity. Various scholars tried to exorcize those spirits but were not successful. The township was traumatized by this situation and eventually the righteous Jew came to visit and asked the townspeople to do certain actions, like bringing Torah scrolls in or near that house, which aroused the wrath of those spirits, who began to scream and complain. The righteous man asked them why they were there and they explained that they were brought into being by the evil words that the couple had uttered in their lifetime. The righteous man succeeded in causing them to leave for good.
The great Torah scholar Nachmanides (also known as Ramban) in his commentary on Leviticus 17:7 maintains that “spirits do not have authority” (control), meaning that they do not have power over what happens in the world, thus there is no need for them in the world. As mentioned above, this is especially so in Israel, the Holy Land.
In truth – our attitudes have a lot to do with the matter. The greater our trust in G-d, the less likely we are to encounter evil spirits, or the evil eye. If a person lives in fear and anxiety he may actually draw such things to himself. There are energies in the world which belong to the realm of holiness, and energies which belong to the realm of unholiness. If a person strengthens himself in a lifestyle of sincerely studying and carrying out G-d’s commandments, (Torah law for Jewish people and Noahide Laws for non-Jews,) he/she is following the right track, and with consistent effort and seeking the right guidance, he/she will attract good energies to him/herself. The person who is not sure where they are going and does not reach out for good guidance, may end up on ‘the wrong side of the tracks’, in a sinister neighborhood.
To conclude on a happy note, I will share another story. In the time of the third Lubavitcher Rebbe, Rabbi Menachem Mendel Shneerson, (same name as the seventh Lubavitcher Rebbe,) there was a disciple of his whose son became deathly ill. The follower traveled to the Rebbe to request a blessing for his child who was in critical condition. He arrived at the Rebbe’s court just before the holiday of Simchat Torah, when there is much joy and dancing in honor of the Torah. He was not able to get an immediate audience with the Rebbe before the holiday, and was sad about that, being greatly concerned about his son. Nevertheless, he decided to participate in the dancing with great joy, since the festival is holy and must not be tainted by personal concerns. Following the festival, the Rebbe told him, “think good and it will be good.” He immediately set out on the journey back home, only to discover that his son’s health had taken a sudden turn for the better at the exact moment that the Rebbe had told him to “think good.”
And it WAS good. From this we learn the power of a positive attitude!