The renowned Kabbalist Rabbi Levi Yitzchak Schneerson, in a 1932 letter to his son the future Lubavitcher Rebbe, Rabbi Menachem Mendel Schneerson, explained the inner meaning of one of the rituals of the Passover Seder—Yachatz—the breaking of the middle matzah. When arranging the Seder plate, we are careful to select three whole matzot. However, as soon as we wash our hands and before even reciting the blessing over these matzot, we take the middle matzah and break it in half. The larger part becomes the afikoman (“dessert”) and is set aside until the very end of the Seder, when it is taken out and eaten in remembrance of the Passover sacrifice eaten while the Temples stood in Jerusalem. The smaller part of the broken middle matzah is returned back to the Seder plate—the k’ara—where it remains partially exposed during the recital of the Haggadah.
Rabbi Levi Yitzchak Schneerson, known as Reb Levik, pondered in his letter, Why look for a whole matzah in setting up the Seder plate, only to break it minutes later?” He answered this question as follows: The larger part is davar gadol (a “large thing,” “great matter,” or “more important matter”), and the smaller part is davar katan (a “small thing” or a “minor matter”). The Talmud explains (in a different context) that davar katan (“minor matter”) refers to the teachings of Abaya and Rava—two primary amoraim (sages of the Talmud)—using this expression as a euphemism for the Nigleh, the revealed portion of the Torah discussed in the Talmud. The davar gadol (“great matter”), the Talmud says, refers to Ma’aseh Merkavah (the “Works of the Chariot”—the mystical prophecy of Ezekiel), a euphemism for the hidden portion of the Torah—the Kabbalah. Reb Levik connects this explanation to the ritual of Yachatz, explaining that the smaller portion of the middle matzah, davar katan, symbolizes the revealed portion of the Torah, the Nigleh (the “revealed”), which is why it remains on the plate partially uncovered and revealed throughout the recitation of the Haggadah. The larger portion of the matzah hidden away until the end of the meal symbolizes the esoteric level of the Torah, Nistar (the “hidden”)—that is, Kabbalah—which is why the afikoman is hidden.
Furthermore, until the eating of the dessert—the afikoman—the Haggadah speaks of the Exodus from Egypt. Following the eating of the afikoman, the focus of the Seder changes to the future messianic redemption. This is the time when the hidden wisdom of Kabbalah will be revealed, which is why at that stage of the Seder, we take the afikoman from the place where it was hidden and unwrap it, revealing it before it is eaten.
Finally, Reb Levik explains that we use specifically the whole matzah before breaking it to emphasize that, from G-d’s perspective, Torah is whole. Only to us, it appears as having two distinct parts—the revealed, Nigleh, and the hidden, Nistar. From G‑d’s vantage point, it’s all one. So, the whole matzah symbolizes the Torah as seen from above (da’at elyon—the “supernal knowledge”), whereas the broken matzah symbolizes the Torah from our perspective (da’at tachton—the “lower knowledge”). Thus far is Reb Levik’s explanation of the Yachatz—the custom of breaking the middle matzah during the Passover Seder, as revealed in the letter to his son, the future Rebbe.
Building on Reb Levik’s explanation, I would like to expand on and generalize these ideas. It seems that the ritual of Yachatz symbolizes not only the Torah in the dichotomy of its revealed and hidden layers, but, more generally, it represents the revealed and hidden layers of reality—both spiritual and physical—and their ultimate unity.
In Kabbalah and the Chasidic philosophy of Chabad, the revealed and hidden worlds are described using the Zoharic terms Alma d’Isgalya (the “revealed world”) and Alma d’Iskasya (the “hidden world”). These terms are allegorically compared to dry land and the sea, respectively. Dryland, most of the inhabitants of which can be seen, is used as a metaphor for Alma d’Isgalya—the revealed world. The sea, on the other hand, hides its inhabitants. Looking at the sea, one sees only its surface. The sea, however, is deep and teams with countless fish and aquatic creatures, mostly hidden from the eye. For this reason, the sea is used as the metaphor for Alma d’Iskasya—the hidden world.
In fact, the splitting of the sea that we celebrate on the seventh day of Passover is explained in terms of the revelation of the hidden realms when Alma d’Iskasya transforms into Alma d’Isgalya. It seems to me that the ritual of breaking the middle matzah—Yachatz—is a metaphor for the dichotomy between the hidden (Alma d’Iskasya) and the revealed (Alma d’Isgalya) in general. Furthermore, from the details of this ritual, we glean that the hidden aspect is always bigger (or greater, more significant) than the revealed aspect of reality. (Recall that the smaller piece of the middle matzah is returned to the plate and remains uncovered and revealed, whereas the larger piece is hidden until the end of the meal when it is eaten for dessert as afikoman.) The hidden layer of reality will be revealed in the messianic era, just as the eating of afikoman signals the shift of the focus on future redemption. Last, the whole matzah selected for Yachatz symbolizes the unity of creation from the vantage point of the Creator. Let us summarize these four aspects of Yachatz that, I contend, could be found in every level of reality:
- Everything has a hidden and a revealed aspect;
- The hidden aspect is always greater (or more significant in some sense) than the revealed aspect;
- The bifurcation of reality into hidden and revealed parts is illusory and exists only in our frame of reference—the view from below. From the Creator’s point of view—the view from above—there is no bifurcation and no dichotomy, and all is one; and
- The hidden aspect will be revealed during the messianic era, when the underlying unity of reality—including the unity of the hidden and the revealed—will be unveiled.
Let us now see how these four aspects manifest themselves in different layers of reality—physical and spiritual.
On the most basic level, the physical world exists in time and space. Both have the same hidden/revealed dichotomy symbolized by the Yachatz ritual. Time naturally splits into hidden and revealed parts, the hidden being the future and the revealed being the past. We lack information about the future, which is why it is the hidden part of time. On the other hand, the past is an open book—all facts related to events in the past are knowable, at least in principle. The bifurcation of time into the future (hidden) and past (revealed) is self-evident. Furthermore, the past is limited because, no matter how old the world is, it is always limited in duration by its current age. Therefore, the past is the davar katan—the smaller “piece” of the timeline. In contrast, the future is unlimited, as the world may exist, at least in principle, in perpetuity. Thus, the future is the davar gadol—the larger piece of the timeline. The future is also “greater” than the past because a plurality—in fact, a great multitude—of various possibilities exist in the future. However, when the future becomes into the present, this great multitude of possibilities suddenly collapses into a single actuality—the events that actually happen. Only this single actuality exists in the past. Thus, as measured by the number of possible outcomes, the future is much greater than the past. The analogy of the two pieces of the broken middle matzah is inescapable and precise. However, the division between the past and the future is not set in stone. On the contrary, this division is dynamic and fluid, with every present moment moving the boundary between the two forward. This hints at the overall unity of the timeline, which is essentially one whole, notwithstanding the ever-changing boundary between the past and the future. This corresponds to the wholeness of the middle matzah before it is broken. The parallel between time and the ritual of Yachatz is now complete.
This parallel allows us to get a fresh view of the philosophy and physics of time. Among different schools of thought, presentism seems to be a commonsensical approach. According to presentism, the future does not exist because it hasn’t happened yet; the past does not exist because it already happened and is no longer happening; only the present moment exists. However, Yachatz-style analysis gives a different picture. Both future and past exist. However, the future is hidden from us (just as the afikoman is hidden during the Seder), whereas the past is not.
Physicists also tend to deny any division of time into past and present because no such division appears in any physics equations. However, the above analysis shows that we should not expect to see the division between future and past in physics equations, because this division is fluid and changes every moment with the flow of time (the time-flux). Still, laws of physics do implicitly contain the trifurcation of time into past, present, and future. Any law of physics is a triplet: the equation, the initial conditions, and the observation. The equation (or the law itself) predicts the future state of the system and, therefore, represents the future. The equations, however, cannot be solved without the initial conditions, which represent the past—the state in which the system was at the initial moment in time (t = 0). The observation can only be made in the present moment, which is why it represents the present. In quantum mechanics, observation or measurement is extremely important as it collapses the wave function, thereby bringing a plurality of possibilities into a single actuality. The initial conditions are known, representing the revealed aspect of time. The equations, albeit theoretically knowable, are not immediately apparent from observation and need to be discovered, which is why they represent the hidden aspect of time. (See more on this below.) The present is the fluid boundary between the two. Thus, the bifurcation between future and past, although not found explicitly in the laws of physics, is implicitly there, fully parallel with the broken matzah analogy. This also sheds new light on Einstein’s special theory of relativity, proclaiming the relativity of time—specifically, the relativity of simultaneity. Two observers in different frames of reference may see the same event happening at different times, so they may not be able to agree on the present time. However, as we said before, the splitting of time into two parts—past and future—is only relative to the observer. Is it any wonder that the present moment—the moment of bifurcation—is relative and observer-dependent? This is a beautiful example of how the Yachatz-style analysis of revealed and hidden layers of reality helps shed new light on the nature of time and the laws of physics.
Space also has revealed and hidden aspects. We cannot really observe space per se—we see only the distances between objects. Having three objects, A, B, and C, we could choose the smallest of the three, say A, as our standard unit of measure, and calculate how many As fit between B and C. This determines the distance between B and C in units of A. This aspect of the space is relational, because it defines space relative to the objects found in it. This is the revealed aspect of space. From the relational point of view, empty space does not exist, because there are no objects relative to which the distances and angles could be defined. However, according to Einstein’s general theory of relativity, empty space does exist. Moreover, vacuum solutions of Einstein’s field equations show that empty space is not flat, but possesses curvature like the surface of a ball. The value of this curvature could be used to map every point of space. We cannot perceive an empty space; we can only detect it indirectly by bringing a test particle into this otherwise empty space and observing that the particle will travel, not along a straight line, but along a geodesic line—the shortest (or straightest) line on a curved surface. This aspect of space is the hidden aspect. Thus, like the middle matzah, space naturally splits into two parts, revealed (distances between objects) and hidden (the imperceptible empty space between objects). It is obvious that empty space is much larger than imaginary lines connecting objects in space, because lines exist in one dimension, whereas empty space contains more dimensions—three for three-dimensional physical space or four for a four-dimensional spacetime continuum. Therefore, the revealed aspect of relative space is davar katan—the smaller “piece” of space. The hidden aspect of empty space is davar gadol—the larger piece of space. This division into revealed and hidden aspects notwithstanding, space remains whole. Thus, the parallel with the ritual of Yachatz holds.
Once again, this parallel helps analyze different approaches to space. According to one of the leading theoretical physicists of our time, Carlo Rovelli, space is purely relational—that is the spatial relations of various objects make up the fabric of space. This philosophy is the backbone of the loop quantum gravity theory co-authored by Rovelli together with Smolin. According to this approach, there is no such thing as empty space. But according to Einstein and others, empty space is the canvas on which our world is drawn, a stage on which the drama of the universe unfolds. Who is right? Both, of course! It’s just that empty space is the hidden aspect of space, whereas the relational aspect is the revealed aspect of space.
In physics, we study the motion of physical bodies and other physical processes. A measurable process, such as observable motion, is the revealed aspect of the process. The law governing the process is the hidden aspect (just like the future, as discussed above in connection with time). Ancient astronomers were able to measure the motion of visible celestial bodies and predict solar and lunar eclipses thousands of years before Isaac Newton discovered the laws of motion. Laws of physics are few, but they are powerful because they predict a great variety of physical phenomena. Therefore, we are going to say that physical laws are davar gadol due to their importance and predictive power. On the other hand, observable phenomena are davar katan, because they have little predictive power and therefore are of less significance. The parallel with the middle matzah holds here as well.
In mathematics, any statement of a mathematical theory, such as the Pythagorean theorem, is the revealed aspect of the theory, as it relates the various elements of the theory by a precise mathematical formula. The theory’s hidden aspect is the underlying axioms that allow one to prove the theorem. For example, Fermat’s last theorem states that no three positive integers a, b, and c satisfy the equation an + bn = cn for any integer value of n greater than 2. It was stated without proof by Pierre de Fermat in about 1637. For centuries, this conjecture appeared correct, since no one could prove it wrong by finding three integers that would satisfy the above expression. However, 358 years later, in 1994, the theorem was finally proven by Andrew Wiles. Therefore, we can say that statements of a mathematical theory are davar katan, whereas the proof of these statements from the first principles (called axioms) is davar gadol. Needless to say, the mathematical theory retains its unity, notwithstanding this dichotomy.
In quantum mechanics, physical objects and systems are described by a wave function that defines the state of a system. The wave function obeys the Schrödinger equation that determines the evolution of the wave function in time. Although the evolution of the wave function is fully deterministic, the predictions of the measurement outcomes are anything but deterministic; in fact, they are completely random. When we measure the state of a system, the results of a single measurement are unpredictable. However, if we repeat such measurements many times, statistically they will conform to the predictions of the Schrödinger equation. This is because the Schrödinger equation does not predict the state of the system but only the probability of finding it in a particular state. Thus, according to the Born rule, the square amplitude of the wave function gives us the probability of finding the system in a particular state (say, finding a particle in a particular area of space). Going back to the single measurement, albeit random, it gives us information about the present state of the system—thus, it is the revealed aspect of the theory. The hidden probability that becomes apparent only after many repetitions of the measurement is, of course, the hidden aspect of the theory. The single measurement giving a random result is the davar katan (a minor matter), as it is of little consequence beyond this particular measurement, whereas the wave function predicting the statistical outcomes of many measurements is davar gadol (a major matter)—just like the broken middle matzah on the Seder plate. The theory remains complete, notwithstanding this dichotomy in full parallel with the Yachatz.
Until measured, a system is in a superposition of states. A measurement collapses the wave function, reducing the plurality of states into a single observed state. After the observation, the single state of the system is the revealed state, whereas the unobserved superposition of states as predicted by the theory before the observation is the hidden aspect of the system. Because there could be many states in the superposition, the system’s state before the collapse of the wave function is davar gadol. Not surprisingly, the single state after the collapse is davar katan. Once again, reality splits into hidden and revealed states, where the hidden state is davar katan, and the revealed state is davar gadol. Reality, however, retains its wholeness despite this apparent dichotomy—just as does the middle matzah on the Seder plate.
On the most fundamental level of physical reality, we find four fundamental forces: the strong nuclear force, the weak nuclear force (beta decay), the electromagnetic force, and the gravitational force. These four fundamental forces neatly break into two groups: the larger group that includes three forces—the strong nuclear force, the weak nuclear force, and the electromagnetic force—and the small “group” that includes a single force—gravity. There are many reasons for this division. The first reason is that the first three forces—strong, weak, and electromagnetic—are described by quantum field theory, known as the Standard Model. The fourth force, gravity, stands on its own (so far, despite decades of trying, no one has been able to fit gravity into the Standard Model or to build a quantum theory of gravity) and is described by Einstein’s general theory of relativity, which stands in stark conflict with quantum physics. The other reason for this division into two groups is the strength of the field: the first three forces—strong, weak, and electromagnetic—are much stronger than the gravitational force. For example, the weak force is 1024 times stronger than gravity! The differences in strength between the first three forces and gravity, which is so weak in comparison, give rise to the so-called hierarchy problem in quantum field theory, which remains unexplained.
Yet another difference between these two groups of forces concerns symmetry. A test particle moves in a gravitational field along a geodesic (the straightest) line in space, curved by mass distribution. The distribution of mass is external to the test particle. The space in which the test particle moves is also external to the particle. This four-dimensional space (the spacetime continuum) has a certain symmetry known as Lorentz (or Poincaré) symmetry. Because it is the symmetry of external space, it is external (“revealed”) symmetry. Indeed, in theoretical physics, the general covariance (symmetry under general coordinate transformations) is called external symmetry. The other three forces—strong, weak, and electromagnetic—are related to gauging the internal symmetries, such as spin (analogous to the angular momentum due to “rotation,” as it were, of the particle). We see, therefore, that the four fundamental forces are split into two groups: a larger group, davar gadol, of three forces that are connected to hidden internal symmetries, and a smaller group, davar katan, comprised of a single force, gravity, that is connected to external symmetry. Once again, reality is broken into two “pieces”—a hidden larger piece and a revealed smaller piece, corresponding to the larger piece of the broken middle matzah hidden for afikoman and a smaller piece revealed on the Seder plate—the analogy is precise.
Wait, but what role does the whole matzah play in this parallel? Physicists believe that at high energies, right after the Big Bang, all four forces were unified in one super force—a perfect analogy for the whole matzah. However, as the temperature cooled a few moments after the Big Bang, the individual forces broke off from the super force, giving rise to the four fundamental forces—a process known as spontaneous symmetry breaking. The breaking of the middle matzah just a few minutes after putting it onto the Seder plate corresponds to the breaking of the super force a few moments after the Big Bang. Furthermore, the breaking of the middle matzah resulting in two uneven pieces can also be viewed as a spontaneous symmetry breaking, which is responsible for the weak and strong forces—deepening the parallel. A unified field theory—the theory of everything, the holy grail of theoretical physics—will reveal the hidden unity of the four forces and will herald the messianic redemption. Once again, the Yachatz parallel sheds new light on this situation, helping us understand why gravity is so much weaker than the other forces and why it is so difficult to unify it with other forces in a theory of everything.
On the spiritual level, this dichotomy between the hidden and the revealed plays out in exactly the same way. Reb Levik, in his letter to his son, traces the breaking of the middle matzah to the division of Binah into two partzufim—Ima and Tevunah. This division plays out on other spiritual levels as well. The matzah on the Seder plate represents a vessel for divine light. The vessel in Kabbalistic terminology is identified with the sefirah of Malchut, which forms the core of the partzuf Nukvah. However, this partzuf splits into two sub-partzufim—Partzuf Leah and Partzuf Rachel. Partzuf Leah is identified with Olam HaMachshava (the “World of Thought”) and Alma d’Iskasya. Partzuf Rachel, on the other hand, is identified with the Olam HaDibur (the “World of Speech”) and Alma d’Isgalya (the “revealed world”). Indeed, in the relationship of thought and speech, thought is hidden and speech is the revelation of that hidden thought. Thus, Malchut splits into two parts—hidden and revealed. Moreover, biblical Leah and Rachel were sisters—with Leah the elder and Rachel the younger. Thus, we could say that Partzuf Leah—embodied by the physical Leah, the older sister—is davar gadol, whereas Partzuf Rachel—embodied by the physical Rachel, the younger sister—is davar katan. Indeed, in the imagery of Kabbalah, Partzuf Leah “stands” on the head of (that is, above) Partzuf Rachel. The separation of Partzuf Leah and Partzuf Rachel is expressed in the physical world by the chasm that exists in the Jewish nation—the conflict between Judah (Leah’s son) and Joseph (Rachel’s son). This conflict will be finally reconciled in the messianic era, when, as the prophet states:
And the word of the Eternal came unto me, saying: “And thou, son of man, take thee one stick, and write upon it: For Judah, and for the children of Israel his companions; then take another stick, and write upon it: For Joseph, the stick of Ephraim, and of all the house of Israel his companions; and join them for thee one to another into one stick, that they may become one in thy hand.”Ezekiel 37:15-17
The unity of the Jewish nation that will be restored in the messianic time is symbolized by the whole middle matzah.
Ultimately, the dichotomy between the hidden and the revealed reflects the perceived dichotomy between the Creator and His creation. The physical world is the revealed aspect of creation, and, being limited, it is davar katan. The invisible Creator, on the other hand, is the hidden aspect of creation. Unlimited and omnipotent, He is the ultimate davar gadol, as it were. Needless to say, there is no dichotomy in the Creator whatsoever, as He is absolute oneness. The dichotomy between the Creator and His creation exists only in our limited perspective. Ultimately, there is no dichotomy between the Creator and His creation, and everything is one. This ultimate unity is symbolized by the complete middle matzah before it is broken. This unity will be revealed in the messianic era, when:
For the earth shall be filled with the knowledge of the glory of the Lord, as the waters cover the sea.Isaiah 11:9, Habakkuk 2:14
 Likutei Levi Yitzchak, Igrot Kodesh (Kehot) p. 231.
 Talmud, tr. Bavo Batra, 134a.
 Amoraim were Jewish sages of the period from about 200 to 500 CE, who followed earlier sages of the Mishnah, called tanaim. The discussions of amoraim were ultimately codified as the Gemara.
 In fact, “sea” and “dry” are not only metaphors for the hidden (Alma d’Iskasya) and the revealed (Alma d’Isgalya) worlds in general, but are directly parallel to two halves of the middle matzah. First, water occupies much more surface of the earth—71%, to be exact—than does dry land, which makes up the remaining 29%. Moreover, the sea extends deep below the surface, whereas dry land is essentially two-dimensional surface (disregarding a mere few inches of depth where some terrestrial animals make their habitat). Thus, the sea, which represents the hidden layer of the realm, parallels the larger piece of the middle matzah—davar gadol—which is hidden away for the afikoman. Dry land, which represents the revealed aspect of reality, parallels the smaller piece of the matzah that remains revealed on the Seder plate. The Rebbe once mentioned that the seas contain vast riches that would benefit humanity to a much greater extent than space exploration. I am of the opinion that before we attempt to colonize Mars or other planets, we should colonize the oceans and the seas, which are much closer and more accessible, and much more suitable to sustain human life.
 As will be discussed in greater detail below, Reb Levik seems to say as much by noting that the breaking of the middle matzah is rooted in the division of sefirah of Binah into two sub-partzufim—Partzuf Ima and Partzuf Nukva.
 Vacuum solutions of Einstein’s field equation leave nonvanishing scalar curvature R, which is the trace of the Riemann curvature tensor.
 The wave function is a complex-valued function defined on Hilbert space that predicts the probability of finding a system in a particular state.
 See more on this subject in my essays, “Four Cups and Three Matzoth,” “Grand Unification,” “Joseph Teaches Pharaoh a Lesson in Fundamental Forces,” “Four Camps at Sea – Four Fundamental Interactions,” “On Rachel, Leah, and Dark Energy,” “Keturah and Hagar III—A Metaphor for Unification,” “Daughters of Zelophehad,” “Unified Field Theory and the Dew of Resurrection,” and “Grand Unification.”
 In his letter, Reb Levik refers to Ima as Binah.