Is Teshuvah Possible?

In that concealed Mind, hidden from all that lives, there arose the thought to create the world. … He was drawing out the world before Him, but it would not stand… until He created teshuvah.

     Rabbi Meir Ibn Gabbai (c. 1520), as quoted from the new book “The Secrets of Creation: Mysticism Meets Science and Art” by Art Green, Howard Smith and Deborah Band (Ben Yehuda Press, 2025)

Science, as it uncovers how the world works, simultaneously reveals the mind of the Creator. Galileo called nature a Divine Book. The Ten Commandments were, after all, written by the finger of God on stone, and thus stone too is included in the revelation. Maimonides compares the devout but ignorant person to someone walking around the palace of the Ruler, while the one who knows science is compared to someone entering through the palace Gate. 

Scientific discoveries make us think about the world in new ways, often forcing us to acknowledge the truth of totally new, even counter-intuitive ideas, concepts that were not known or even imagined before. Evolution and quantum mechanics are just two such examples. Modern science directly confronts the issue of free will, and similarly it can help us rethink our ideas about the real world, how we act in it, and our religious and moral behavior. ¹ (If the following discussion contains any concepts in physics that are unfamiliar to you, or if you just want to know more, please refer to my book “Let There Be Light: Modern Cosmology and Kabbalah, a New Conversation between Science and Religion,” which has more detailed descriptions and explanations written for the layperson.)

Let me briefly restate the problem. We hold strongly to two opposite and incompatible beliefs! The first is that we have free will – for example, to decide to raise our hand, and then to do so. The second is that every effect has a necessary and sufficient cause – a “reason.” For example, our brain directs our hand to rise when neurons activate the muscles, and those neurons are in turn switched on by electrical impulses, and so forth. Free will is just an illusion, like dreams or optical illusions. Absolutely everything in the real world is the result of deterministic processes.

Indeed, many scientists trace the many steps of cause-and-effect all the way back to the Big Bang. Every action is the necessary result of a previous event. There is no freedom to choose. But if free will does not exist, then neither does the possibility of teshuvah. 

Pretty much all modern scientific and rabbinic sources are in agreement on this. In truth, teshuvah is not possible.

However, although Chazal recognize this conclusion, they nevertheless assert, as did Rabbi Akiva:

הַכֹּל צָפוּי, וְהָרְשׁוּת נְתוּנָה — “Everything is foreseen, yet we have free will (‘permission’).”  (Pirkei Avot 3:15)

There is something miraculous about free will. This is the basis for the Talmudic and midrashic observation, echoed by the Kabbalah and in the above quote by Ibn Gabbai, that teshuvah is an impossible feature of this real world – but since it exists, it must have been created before the world and its laws. 

Modern scientists and philosophers are not so sure.

Here are some facts about the real world to consider. In our deterministic world of cause and effect, interactions can be complicated. It is often not possible to predict precisely what will happen. The study of this behavior is called chaos theory. Weather is a good example: no matter how advanced our models and computers become, it will never be possible to predict exactly the weather beyond more than a few weeks, because even miniscule changes to the initial atmospheric conditions can lead to dramatically different results. This is sometimes called the Butterfly Effect, as coined by Ed Lorentz, who first described it precisely. It had already been long known and proven by mathematicians that while the motions of two bodies can be perfectly calculated, the “three-body problem” is, in principle, not possible to solve precisely. Thus, even the future orbits of the planets (including the Earth) in the solar system are imprecisely known beyond some millions of years. 

However, an inability to predict the future is not at all the same thing as having free will to do what you want. Chaotic systems are fully deterministic. Still, it is worth noticing that Rabbi Akiva does not say, “Everything is predetermined, yet we have free will.” His comment about being foreseen, like the approach of most other rabbinic authorities, is about knowledge of the future and not about what has been determined. “Everything is foreseen (known)” – but maybe they are still determined (forced).

There is one (and only one) known process, quantum mechanics, that does not quite behave deterministically. Since its discovery about 100 years ago, quantum mechanics has become the most successful theory ever, ultimately responsible for the modern technology used in everything from your computer and phone to your lightbulb, and able to explain nature from the working of the Sun to the chemistry in your genome. It has never been found wrong, and literally millions of scientists, engineers and technical experts have been relying on it and testing it for decades.

It is fundamentally mysterious, however, because although it works, physicists do not understand why. It also makes deterministic predictions, but these predictions are only about the “wavefunction” of a thing – how the probability of its having any given property evolves in its encounters. As an object interacts with others over time, the changes to its wavefunction can be calculated and predicted. However, when the interaction ends and a measurement is made, its wavefunction – a set of probabilities – somehow ends up at random in only one form of the many that were possible, and this is what becomes real. This is called the collapse of the wavefunction.

Physicists have tried for 100 years to rid quantum mechanics of this bizarre feature – random outcomes when causes are identical. Einstein did not believe it. It has been suggested there are hidden properties of matter – some feature we do not know about that determines outcomes that otherwise appear to be random but that, if we knew it, would show that the behavior is actually deterministic. But multiple experiments over many decades have conclusively shown most such suggestions are just plain wrong. The Nobel Prize two years ago went to leaders in this research. Some scientists imagine this indeterminate (random) feature of quantum mechanics leaves room for free will, and many argue then that the brain must use quantum processes to enable free will. But others point out that randomness in outcomes in no way enables choice or free will! And remember, quantum mechanics has other related features that are mysteries – for example, the nature of that collapse of the wavefunction (think of the Schrödinger Cat paradox.) 

One last topic to ponder is the multiverse. One famous proposed “solution” to the paradoxes of quantum mechanics has all possible alternatives becoming real, then only one of them randomly happening. In this picture, each interaction results in the universe spinning off into innumerable universes – a multiverse. A great many physicists and philosophers find this explanation for quantum mechanics, however bizarre, to be the most convincing one. 

Analogous proposals postulate the existence of a multiverse from the details of the theory of the big bang, which perhaps can spawn many universes, or from the nature of an infinite universe. Free will, then, would be the outcome in one particular universe, even as it leaves determinism the operating principle that generates all the other universes. 

This option also seems unsatisfying, but it has the advantage of being compatible with the rabbinic view which, in their struggle to understand the perfection of this world, asserted that God created and destroyed many worlds – a multiverse – before settling on this world balanced with justice and mercy…. and with teshuvah.

Modern scientific ideas about free will are very much unsettled, in part because the nature of consciousness itself, the source of our illusion of free will, is also mysterious and debated by neurobiologists, philosophers, and others. But as we struggle personally with what it might mean to at least try to do teshuvah, or not, I hope this summary of some of the modern perspectives will provide useful insights. 

Shana Tova!

(This post is part of Sinai and Synapses’ project Scientists in Synagogues, a grass-roots program to offer Jews opportunities to explore the most interesting and pressing questions surrounding Judaism and science. Howard Smith is a senior research astrophysicist at the Harvard-Smithsonian Center for Astrophysics, retired teacher from the Harvard Astronomy Department. He is the author of Let There Be Light: Modern Cosmology and Kabbalah: A New Conversation Between Science and Religion, in addition to being an author on over 400 scientific journal articles and the forthcoming book The Secrets of Creation: Mysticism Meets Science and Art. He held an event at Temple Beth Abraham in Nashua, NH in December 2022, and gave a Qabbalat Shabbat talk on April 5, 2024 at Temple Israel of Boston.)