Before we venture out of our own universe in search for life, we should perhaps begin our discussion with life on other planets in our own world.

As is explained in Are human beings the only conscious beings in the universe, while there may very well be life on other planets, these lifeforms would not be able to have free will, since free will is possible only where there is Torah, whereby the Creator offers His creatures more than one possibility and asks that they make the appropriate choice.

That said, we can now turn to the question of parallel universes.

Different people mean different things when they talk about parallel universes. One of the more popular concepts is the Many Worlds Interpretation (MWI), in which there is a large number of universes, and everything that could possibly have happened has occurred in some other universe or universes. This theory and variations of it have been greatly popularized in science fiction.

If we analyze this theory, it leads to the possibility of one meeting their other self from some other dimension. Since we have already precluded the possibility of other intelligent lifeforms with capacity for free will to exist in any other place besides for our own world, we are forced to say that this type of parallel universe does not exist. For in order for this theory to work, these separate worlds have to spin off into their own respective timelines, with their very own free will decisionmaking process.

However, if the question is whether there other worlds or realities, then the answer is yes.

According to Kabbalah, all of existence can be divided into four worlds, known as Atzilut (World of Emanation), Beriah (World of Creation), Yetzirah (World of Formation) and Asiyah (World of Action—our world). Although they are referred to as worlds, in reality these aren’t separate planets or galaxies. Rather, they exist right here together with us, but in another plane of reality.

Each of these worlds is really about the degree of G‑dliness that is revealed on each plane. To see more about these other worlds, see Where Are All the “Worlds”?.

Furthermore, while we have precluded the possibility of other universes spinning off from ours based on alternative possible choices, in a certain sense even when we have not done an action but merely said we would do one, the action has already been taken in the World of Speech.

We are told the story of two Mezhibuzh citizens who were involved in a bitter dispute. Once, while they were angrily having it out in the local synagogue, one shouted at the other, “I will tear you apart like a fish!”

Rabbi Israel Baal Shem Tov, who was in the synagogue at the time, told his disciples to form a circle, each taking the hand of his neighbor, and to close their eyes. The Baal Shem Tov himself closed the circle by placing his holy hands upon the shoulders of the two disciples who stood nearest to him. Suddenly, the disciples cried out in fright: they saw the angry man actually ripping his fellow apart, just as he had threatened!

No potential ever remains unrealized. A person’s every act, word, and even thought has an effect. At times the effect is concrete and tangible; at times it is more subtle, and can be discerned only by a finer, more spiritual eye.

So, in the end, I guess the answer to the question depends on what precisely is meant by parallel universes.

Let me know if this helps.

Wishing you all the best,

Rabbi Yehuda Shurpin