The Role of the Observer in Halachah and Quantuum Physics

The idea to write an article exploring the parallels between quantum physics and halakhah (Jewish Law) was inspired by a discourse of the Lubavitcher Rebbe on Shabbat Parashat Shemini in 1985, in which the dependence of physical reality on testimony of witnesses was discussed. The second author of this paper was present for the above discourse and the parallels between the ideas discussed by the Rebbe and the views of quantum physics struck him. He shared his impressions with the first author and that is how work on this article began.

According to the philosophy of quantum physics, actual physical reality can exist (in the scientific meaning of the term existence) only as a result of measurement. When not being measured, the universe is in a quasi-real state amenable to description only in terms of probabilities and not facts. Some eminent physicists argue that the measurement must be performed by a conscious entity. According to this view, it is only measurement performed by a conscious being which can bring the universe into full reality.

This paper explores various fundamental perspectives in Jewish philosophy and halakhah that reveal parallels to this quantum world-view. These parallels pertain to ontology, which addresses the essence of existence, as well as to epistemology, which deals with criteria for knowledge. In the first section, we present a very brief summary of the relevant aspects of Jewish philosophy and halakhah. These include the Jewish view of the Creation. Man’s purpose, and man’s unique characteristics; and finally the halakhic methodology for the establishment of fact. All of these are related by the common theme of determination of reality via observation performed by a consciousness.

For many years there was a debate among scientists regarding the nature of light. Certain phenomena seemed to indicate that light is a wave, while others pointed to its having a particle-like nature. The debate was stilled early this century when it was realized that all entities can be considered to be both waves and particles - some physical conditions cause a manifestation of the wave-like properties of these entities, and some cause a manifestation of their particle-like properties. This duality became one of the fundamental concepts of the newly-developed quantum physics.

The duality concept arises as follows. If one were to eject an electron from an electron gun and run it through a slit of some sort, one would expect that since an electron is a particle, it would continue straight in a flat trajectory and reach a screen or a detector directly opposite to where it emerged. On the other hand, if one has a water or light wave, the waves bend as they traverse and opening, and form a complex pattern on the other side. When water or light waves are passed through a double slit, it has been shown that the resulting pattern can be attributed to the fact that each wave passes through both slits. It was shown experimentally, however, that even particles, such as electrons, form the same patterns as do waves, as though each particle passed through both slits - which seems impossible to our intuition! This led to the understanding that all entities in the universe are both waves and particles.

Prior to the advent of quantum physics, science believed that every event in the universe occurred as an inevitable and necessary result of previous events. The state of the universe at any one instant was believed to be totally determined by the states of the universe in the past, and in turn the present state totally determined what all future states of the universe would be.

Quantum physics, introduced at the beginning of the twentieth century, brought with it a drastic change in this viewpoint. Each event was now understood to be able to occur in a number of ways, with the actual way that it does occur left to “chance.” Despite the fact that chance “ruled” each individual event, however, when numerous similar events occurred, the pattern that emerged resembled the results one would have expected using pre-quantum physics.

That is, each individual event, though occurring “at random,” nevertheless contributes somehow to a pattern, in the aggregate, which can be determined beforehand. This combination of random and determined behavior is called here probabilistic determinism or probabilistically determined randomness.

Much inquiry was directed to the question of whether the chance aspect was only apparent - i.e. due to our lack of sufficient scientific knowledge and adequate instrumentation - or if it was an actual physical requirement. With the accumulation of more experimental evidence it was shown that, indeed, the nature of the physical universe appears to be such that intrinsically, at the most fundamental level, events are probabilistic and not deterministic.

The mathematical description of a quantum system is that of a wave which corresponds to the system being in all possible states simultaneously - a “superposition of states.” (The physical interpretation of this wave is that of a probability distribution for the result of an individual efvent in an ensemble of cases or particles.) For example, in the case of the slit, each particle is represented by a wave function that corresponds to its going through both slits at all possible angles. However, when we look about us we always see unique states - for example, the unique impact point of the electron on the screen behind the slits.

Even the most subtle measurements on the particle while it is in flight, to determine its exact path have been shown experimentally and theoretically to so disturb the path that the pattern is lost. Wheeler’s 'delayed choice' experiment has shown that one can even perform the measurements after passage through the slit, and retroactively affect the outcome. Therefore one cannot attribute a unique “physically real” path to the particle, even in theory - it is in a superposition state.

Thus there is a vast difference between the system prior to measurement - it is in a superposition of all possible states - and after measurement, when it is in a unique state. It can only be the act of measurement itself that causes this drastic change. It is counterintuitive because out observations of the universe about us are measurements, and we therefore always see only unique states, not superpositions.

Prior to its measurement, an event can occur in a number of ways and actually does so in some sense. Without measuring the state of a particle, we cannot say, “It is in some particular state, which is, however, as yet unknown to us.” It is not in some particular state. Instead, it is (in some sense) simultaneously in all the possible states in which it can be! Indeed, even after measurement is made, and the particle is found to be in a particular state, we cannot then say that the particle was in that state all the time - no! It had no definite state until one measured it. Our measurement forces the universe to assume one definite state from among all the possibility-states it is in prior to the measurement! This is usually called “the collapse of the wave function into reality.”

This surprising, even bewildering, property can be interpreted as saying that the universe can emerge into reality only as a result of its measurement! In a way this is trite and in a way it’s radical. It is trite in the sense that for a at least two centuries philosophers such as Berkeley and the positivists have explored the idea that reality is only set by our consciousness of it, because we can perceive things through the senses. It is radical, however, in that this result has now been achieved by physics. Therefore, what is true in the realm of words and ideas has been shown by physics to be true of physical reality as well: the actual thing itself is not set until it is measured.

From the preceding discussion, we can make the following summary: All entities in the universe have a dual nature, one material and localized (particulate) and one nonmaterial and non-localized (wavelike). The universe, or any subsystem of it, is capable of being in two (or more) mutually contradictory states simultaneously. Saying that the universe is uniquely in one state is just as invalid as saying that it is in the other state. However, a decision can be made between the two by having a measurement made of the situation. Both views are partially correct, but only until the measurement is made. After that, only one becomes correct. However, this does not imply that it was always the correct one; there was no “correct” state until the measurement was made.

What is the active factor in a measurement which causes this emergence into reality? According to some leading physicists, this factor is consciousness. The great mathematician John Von Neumann, who provided a rigorous mathematical foundation for quantum mechanics, believed that only a human consciousness can collapse the wave function.

It follows that the quantum description of objects is influenced by impressions entering my consciousness…. It follows that the being with a consciousness must have a different role in quantum mechanics than the inanimate measuring device.

Thus, according to “quantum metaphysics,” a consciousness is indispensable to the universe if it is to emerge into reality. Physical reality can be said to exist only as a result of our presence within it or, more precisely, as a result of our perception of it.

Wheeler has constructed a fascinating diagram to illustrate this concept. Explaining the diagram, he writes: “Beginning with the Big Bang, the universe expands and cools. After eons of dynamic development it gives rise to observership. Acts of observer-participancy in turn give tangible reality to the universe not only now but back to the beginning.”

A free-willed decision, in order to be truly free, has to be unconstrained by the laws of nature and not determined by any physical phenomena. Hence free will must be neither the result of deterministic processes, nor the result of random processes occurring in accordance with the natural order of phenomena. Hence if the universe contains a free will, this free will must operate via interactions which transcend both the determinism of classical physics and the randomness of quantum physics. Free will is then unique in this respect.

If some entity exists which can collapse the quantum wave function, then it is reasonable to postulate that this entity has to be a free will, since, as we just discussed, only free will transcends quantum randomness, as it transcends nature in general.

Since a consciousness can affect the universe only if it has a free will, and a free will is by definition unthinkable without a consciousness, we will assume in the course of further discussion that free will subsumes within itself the concept of consciousness.

We will now try to apply the conclusions we reached above to the question of the existence of the universe. As we saw, according to quantum metaphysics, the universe can emerge into reality only when it is observed by a consciousness. This consciousness possibly must function in a nonquantum fashion in order to “collapse the wave function.” The only such nonquantum factor in the universe is free will. Thus, we postulate that it is the presence of a free-willed, conscious being which enables the universe to emerge into reality.

According to Jewish thought, the true reality is the spiritual realm, the physical cosmos being God’s precision-crafted instrument for achieving spiritual goals. Indeed, the physical universe is a shadow of the spiritual world, the illusion perceived by limited beings who are in contact with the spiritual cosmos but can directly sense and perceive only its shadow. Human free-willed moral choice connects the two realms, and this moral activity gives meaning to the existence of the universe.

Thus, since the true reality of the universe is the spiritually meaningful aspect, it should not be surprising that the emergence of the universe into reality is so intimately bound up with the emergence of those beings who endow physicality of meaning. Furthermore, once this connection is understood, it is most appropriate that the very characteristics of man which allow the emergence of the universe into reality (i.e., his free-willed consciousness) are the very same characteristics which endow it with meaning. We can thus see the fundamental interrelationship between meaning, purpose, free will, consciousness, and the very nature of reality (and how this is reflected in Creation).

We have seen that according to quantum (meta)physics, reality is established via the observation of a (free-willed) consciousness. In addition, we have shown hat according to Jewish thought, free-willed choice gives the universe meaning and is thus the “motivation” for the very existence of the universe. We will now explore how the nature of everyday Jewish law is correlated with this radical conception of the reality of the universe.

According to Jewish tradition, the Torah is the “blueprint” which was used by G-d in creating the universe. Moreover, G-d is continually renewing Creation - re-creating the universe at every moment - by interpreting the blueprint for the re-creation of the universe at that instant. These statements pertain to a more abstract form of Torah, to a Torah that exists spiritually in the form of “black fire on white fire.” However, once this Torah was translated into human terms and given over to man at Sinai, the prerogative of its interpretation and application rested solely with man; it is man’s responsibility and his alone. And through involvement with Torah, man actually becomes a partner in the continuous renewal of the cosmos.

In our universe, the operative concepts are “free-willed conscious choice,” not “nature,” i.e. objective scientific fact. It is the former which causes the latter to emerge into existence (collapse of a probability wave). Thus, it will not come a surprise that, in Jewish law, free-willed conscious moral choice rules over the “laws of nature,” rather than vice versa.

The true reality is the spiritual one. The physical is in existence only to serve the spiritual. The entire physical universe is an artifact created by G-d. Man us a precisely crafted instrument designed to interact with the physical universe in ways which have the potential to achieve spiritual goals unattainable without the vehicle of the physical. Thus, the physical is of central importance, but only as a means: It can have sublime beauty and dignity, but only by virtue of its ability to achieve in the spiritual realm. Thus the human body, rather than being a hindrance to spirituality, is a potentially holy physical tool which can control the spiritual.

There are three ways by which man determines halakhic reality: by determining which one of several rabbinic opinions shall be authorized for implementation; by determining which of several scenarios (having halakhic relevance) is the factually correct one; and by determining the reality itself, i.e., forcing the reality to conform with the halakhic opinion.

Since the spiritual reality is determined by man, there is no paradox involved in two mutually contradictory results being both right, as long as they represent two human opinions arrived at through religiously legitimate means. The Torah also gives us rules for deciding the actual path to take when we are presented with two or more valid opinions, for example, the principle of decision by majority. Once one of the paths has been accepted by rabbinical authority, it alone becomes the only viable path of action. Even though the other path is still theoretically correct, it becomes absolutely unacceptable as an actual path as soon as the religious reality is decided in favor of the other.

For example, the dates for Jewish holidays were set according to rabbinical ruling based on observation of the moon and on calculations. One year the date for Yom Kippur (the holiest day of the year) calculated by Rabbi Yehoshua differed by one day from the date arrived at by Rabban Gamliel. Since Rabban Gamliel was the nasi (chief justice), the ruling followed his view. In order to prevent anarchy, he then ordered Rabbi Yehoshua to come see him on the day Rabbi Yehoshua considered to be Yom Kippur - and to do so in a manner forbidden on Yom Kippur. This would prove that there was only one authoritative ruling. Rabbi Yehoshua came, violating what he considered to be the holiest day of the year, in deference to Rabban Gamliel’s view. Rabban Gamliel then told him that he considered Rabbi Yehoshua to be his superior in wisdom and learning, but that as nasi his word was nevertheless law. Thus, even though Rabbi Yehoshua’s view was possibly more logically valid that that of Rabban Gamliel, as soon as the decision was made in favor of the other view, his own ruling became totally unacceptable as religious law, and the day he considered the holiest ceased to be so.

We have just seen that two conflicting opinions can both be considered valid, yet that only the majority opinion is accepted as normative. This is an example of the simplest level at which man determines the halakhic reality, i.e., that of determining which of several opinions shall be accepted as normative halakhah. We will now present examples of the other two levels on which this is true: disclosure of factual reality and causation of factual reality.

Disclosure of factual reality: In the same mishnah discussed above, Rabbi Akiva brought proof from the Torah that even if the court set a festival on the incorrect day through its own error, the declaration was religiously valid. The following mishnah relates that even if all the people of Israel, including all the court justices, saw the new moon and/or received the testimony of the witnesses, if the court did not declare it as the new moon (by the day’s end), the new moon was considered to begin the next day.

Even when Halakhah seemingly depends on objective physical reality, such as temporal sanctification at the time of the new moon, what actually determines the Halakhah is the decision/measurement made by man (in this case, the court ruling), even though the physical facts seem to present a contradiction. Neither nature nor super-natural events can usurp the prerogative of man in deciding Halakhah and thus the spiritual reality. This can be seen graphically in the account presented in the following narrative from the Talmud.

Rabbi Yehoshua and Rabbi Eliezer were arguing a point of religious law. Rabbi Eliezer was unable to convince Rabbi Yehoshua of his point, and so he tried to convince him by using miracles. He said, “If I am right, let the stream run uphill.” And it did so. This, however, did not convince Rabbi Yehoshua. “If I am right, let the wall bend,” declared Rabbi Eliezer, and the wall indeed bent. Rabbi Yehoshua, however, remained unconvinced! So Rabbi Eliezer called upon Heaven itself to decide the matter. He said, “If I am right, let Heaven prove it.” Indeed, a voice came from Heaven and declared, “What do you want from Rabbi Eliezer? The ruling is always in accordance with his views.” At this point, Rabbi Yehoshua arose and quoted the Torah, saying, “It [the Torah] is not in Heaven.” By this he meant that it is man - not physical law or even Heaven - who decides spiritual reality. That is, he did not dispute the fact that Heaven had decided in favor if Rabbi Eliezer (and that probably this meant that “nature” favored him as well ); rather, he claimed that Heaven had already delegated the authority in such matters to man alone!

The most far-reaching example of such philosophy can again be found in the Talmud. There we are shown quite clearly that neither the inhabitants of the spiritual realm nor G-d Himself defines halakha; only man can do so. A debate about a religious ruling was taking place between members of the “Heavenly College” (the souls of deceased saintly rabbinical scholars) and G-d Himself: God held to one view and the members of the College to another. The college then decided that in order to reach an authoritative ruling, neither G-d nor Moses could decide, but rather that the living rabbinical authority (Rabbi Bar Nachmani) must decide.

The Talmud also tells us what G-d’s view of all this is: At the end of the case with Rabbi Yehoshua and Rabbi Eliezer describes previously, Elijah the Prophet is quoted as reporting that G-d was immensely pleased with man’s understanding of his role in determining religious reality, and that He even laughed with joy, saying, “My sons have bested me, my sons have bested me.” Thus on questions of halakhah and spiritual reality, the world, the Heavens, and G-d Himself all defer to man, though he be incomplete and limited.

Halakhah and the Causation of Reality: Since the Torah is the blueprint of Creation, man’s interpretation of it can have cosmic effect; halakhic ruling causes physical reality to emerge and even change so as to conform with the blueprint from which it was created. Thus and extremely potent level on which man can determine physical reality is that of halakhic decision. This astonishing concept is referred to in a famous passage in the Jerusalem Talmud. In order to understand the passage, one must be familiar with the concept of the leap year in the Jewish calendar.

A Jewish leap year involves the addition of a thirteenth month to the twelve-lunar-month year, in order to correlate it with the solar year. If a child is born in the middle of the last month of a non-leap year, then the month of birth is both “the twelfth” and “the last” month of the year. During leap years, when the twelfth month is not the last month, it is not obvious which month is the child’s birth month: the last (thirteenth) month, or the twelfth (second to last) month. The Talmudic ruling is that the birthday is on the last (thirteenth month).

The passage in the Jerusalem Talmud which we mention above concerns physical changes in the body of a child involving a lessened ability of the body to regenerate certain tissues; this change is determined as occurring at the conclusion of the third year of life. Thus, if the child’s birthday is, for example, on the fifth day of the last month, then in the third year, on the fifth of the last month, the physical change occurs. However, if at the end of the month, after the change has taken place, it is decided by the court that a thirteenth month will be added to the year, the third birthday according to halakhah has not yet occurred (it will occur only on the fifth day of this newly added thirteenth month), and thus the physical change should not yet have occurred. According to this Talmudic source, the physical change will, in this circumstance, actually reverse itself in conformance with the halakhic decision! (If an observation is already made, the reality is “frozen” and cannot be changed retroactively by a later observation; it can, however, be changed if no observation is made.)

For another instance, the famous Rogatchover Gaon once indicated a similar philosophy regarding the ability of halakhah to determine physical reality. A woman once came to him with a defective slaughtered chicken to ask whether or not it was terefah (an animal with a terminal disease or fatal defect that renders it not kosher). The chicken seemed to be a clear-cut state of terefah, yet the Rogatchover’s students noticed that their rabbi spent hours checking it, consulting books, thinking and so on, rather than spending the usual few minutes. They were astounded that this great genius would waste his time on such a trivial matter instead of simply buying the chicken from the woman and throwing it out. In the end, the Rogatchover was able to find a way to reach the halakhic decision that the chicken was not terefah, i.e., disease was not fatal according to the halakhic definition of “fatal.” The students were stupefied at the exertion of such genius over such triviality.

The next day, a woman came to the Rogatchover wailing and sobbing. Her husband was deathly ill, she cried, asking the rabbi for help. The Rogatchover asked the woman what was wrong with her husband. She described precisely the disease which afflicted her husband. The Rogatchvoer answered thus: “Don’t worry—only yesterday I examined a chicken with the identical disease and I ruled that it was not a terefah - your husband is therefore not deathly ill and will recover!”

The biblical sources given for this far-reaching concept are passages in Psalms and Isaiah, whose hidden meanings had been passed down along with the text from generation to generation. For example, in Isaiah 44:24-26, we read: “I am the Lord that makes all things; that stretches the heavens, alone; that spreads abroad the earth by Myself; that frustrates the omens of impostors, and makes diviners mad; that turns wise men backward, and makes their knowledge foolish; that confirms the word of His servant, and performs the counsel of His messengers".

God created the universe ex nihilo, but has left to man the fashioning of this raw material, as indicated in the traditional interpretation of the passage: “For then He rested from His work, which He created to be fashioned.” (Genesis 2:3)

We can now compare the halakhic view of reality with that of quantum physics. According to the Talmud, two or more logically valid halakhic rulings may be consistent with the available facts. Indeed, two independent valid viewpoints can be diametrically opposed and mutually contradictory. Halakhah allows either one to determine the reality in principle but will accept only one of the possibilities in actuality.

The analogy between this conception and the idea of the multiple possibilities for reality prior to a “measurement” in quantum physics is now obvious. Although both are the (living) words/realities of (the living) G-d, only one can determine reality. Also, even though all entities can be measured to produce the characteristics of either waves or particles - both are living reality - only one aspect by itself can be seen “statistically” as the result of an actual measurement.

Furthermore, just as according to quantum physics (or metaphysics) nature has delegated to man the ability to determine the nature of physical reality within the limitations of natural law, similarly, according to Torah, God, the Creator of nature, has delegated to man alone the ability to determine the nature of spiritual reality, within the limitations of halakhah. Spiritual reality then influences the physical. Of the two levels, the physical is merely the means to the spiritual end. Thus the determination by man of spiritual reality is even more fundamental than is his determination of physical reality. So, too, it is man’s spiritual qualities (free-willed consciousness) which are more fundamental than these physical qualities.

As illustrated in the previously cited instances, it is up to man to use his own limited sense of right and wrong, guided by Torah criteria, to determine the halakhah and thus to determine reality. Halakhah is the guideline for the Torah way of life, the way to achieve one’s purpose - and it is this purpose which also gives meaning to the universe. Since it is man’s consciousness and free will which invest his choices with the possibility of meaning, it is therefore only free-willed consciousness which has the possibility of conducting reality-determining observation and measurement.

Nature by itself is powerless to achieve self-realization; man is required to bring both himself and the universe into reality. Thus nature cannot determine halakhah. Similarly, G-d Himself does not decide halakhah; it is man’s prerogative and sole responsibility. Man, alive and physical and yet spiritual as well, albeit limited and fallible - or perhaps because he is limited and fallible - is uniquely qualified, by virtue of his possessing a free-willed consciousness, to determine the nature of physical and spiritual reality.

As we have seen, quantum physics connects ontology (being) with epistemology (knowing), and quantum metaphysics postulates that the universe can emerge into true physical existence only when there are (free-willed) conscious beings in it. According to this scenario, man is not a random product of the universe but is rather a necessary condition for the very existence of the universe. In addition, since the universe can emerge into true physical existence only when free-willed conscious man is present within it, there is no true physical reality to any time prior to the emergence of the first free-willed conscious man. According to Torah, this man was Adam.

Of course, other theories have been advanced regarding the emergence of man. However, these by definition relate to a time prior to the emergence of conscious individuals. According to the approach of quantum physics explored here, these theories cannot relate actual physical historical events since there were no such actual events prior to the emergence of free-willed conscious beings.

Whether or not one accepts the Torah as being able to provide infer no matters inaccessible to scientific inquiry is in itself a matter of free-willed choice. However, if events “prior” to the emergence of the first free-willed conscious being are undefined scientifically, then it is only to be expected that there will be differences between the description made of the emergence of this first free-willed conscious being by a source limited by quantum physics - such as man and his theories - and the description made by a source originating outside of physicality - such as the Torah.