In the biblical story of the creation of Adam, the Torah states:
Then the Eternal G‑d formed man of the dust of the ground, and breathed into his nostrils the breath of life; and man became a living soul.Genesis 2:7
The word translated into English as “soul” in the original Hebrew is nefesh. This is the first and the lowest level of the soul given to Adam. The taxonomy and anatomy of a soul in Judaism are quite complex. Original biblical sources speak of three levels of the soul: nefesh (“soul”), ru’ach (“spirit”), and neshamah (“breath”). The Kabbalah speaks of the five levels of the soul: nefesh, ru’ach, neshamah, chayah, and yechidah. This is based on classical rabbinic sources. As stated in the midrash, “By five names is the soul called: nefesh, ru’ach, neshamah, chayah, yechidah.”, One of the earliest mentions of chayah and yechidah is found in the Zohar section Rayah Nehemnah:
“And you shall love the Eternal, your G‑d, with all your heart”—meaning the body—“and with all your nefesh” – meaning the soul (neshamah), as it has five name, neshamah, ru’ach, nefesh, chayah, yechidah—“and with all your might”—meaning all your money.
Later, the Arizal also spoke of five levels of the soul, as recorded by his principal student, Rabbi Chaim Vital. However, the concept of the five levels of the soul later took the center stage in the philosophy of Chabad, as expounded in its principal book, Tanya, and later works.
The relationship between these five levels of the soul is illustrated in Kabbalah with the metaphor of the glassblower. According to this metaphor, we imagine an artisan glassblower who decides to create a beautiful glass vessel. The unique creative idea in the artisan’s mind corresponds to the level of yechidah—the unique (singular) essence. The glassblower himself corresponds to the level of chayah—the living essence. The process of expanding the lungs of the glassblower, gathering the air (inhaling), corresponds with the level of neshamah—breath. The air rapidly moving down the glassblower’s pipe corresponds to the level of ru’ach (wind). The air coming to rest (nafash) in the glass vessel on the other end of the pipe corresponds to the level of nefesh—the soul that rests in a body.
This metaphor is deep and insightful. Kabbalists stress that this metaphor allows us to see the parallels between the letters of G‑d’s proper name, the Tetragrammaton YudHehWawHeh (Y‑H‑W‑H), and the five levels of the soul. The apex (kotz, or the upper thorn) of the yud corresponds to the initial creative idea, a flash of inspiration, and is a parallel to the level of yechidah—the unique essence, the singularity. Yud itself corresponds to the living being—the glassblower (a metaphor for the Creator)—and thus also corresponds to the level of chayah—the living essence. The first heh, which visually is an expansion of yud (which is little more than a dot) into the four directions on the plane, הּ <— י, corresponds to the expanding lungs of the glassblower gathering air. This corresponds to the neshamah, which comes from the word neshamah (“to breathe” or “to inhale”). The next letter in the Tetragrammaton is waw, which is written as a vertical line (ו). This letter corresponds to the glassblower’s pipe. In turn, it also corresponds to the level of ru’ach (“wind”), because the air moves rapidly like the wind through the pipe of the glassblower. Ru’ach also means “breath,” corresponding to the air going through the pipe—the glassblower’s exhalation. The last letter of the Tetragrammaton is the second letter heh. As explained above, heh is an expansion of the dot—the visual form of the letter yud. This corresponds to the air expanding in all directions at the end of the glassblower’s pipe to create, through inflation, a vessel from a blob of molten glass. The air finally rests in the vessel, which corresponds to the level of nefesh (which means nafash, or “to rest”). This is the lowest level of the soul that rests in the body.
Let us summarize the glassblower metaphor in the following table:
|Letter of the Tetragrammaton||Element in the Glassblower Metaphor||Level of the Soul|
|kotz—the apex (thorn) of the yud||creative idea||yechidah|
|heh||expanding lungs of the glassblower||neshamah|
|heh||air expanding the vessel and resting in the vessel||nefesh|
Table 1. The glassblower analogy
And now we shall examine the five levels of the soul in greater detail.
Nefesh. Nefesh (“soul,” psyche) is the first and the most basic level of the soul. Even animals possess this lowest level of the soul. We learn this from the verse in Genesis:
Only flesh with the soul thereof, which is the blood thereof, shall ye not eat. (Genesis 9:4)
In Jewish metaphysics, nefesh is what creates the distinction between a live body and one that is not alive. As the lowest level of the soul, this level actually connects and interacts with the material body. It’s where the rubber meets the road, as it were. Nefesh is responsible for life itself in its most basic form. Thus, nefesh is what animates the body and is associated with the basic instincts of human beings (as well as animals) and their motor functions.
The word nefesh has an interesting etymology. The word comes from nafash, which means “rested.” We learn this from this verse in Exodus:
It is a sign between Me and the children of Israel for ever; for in six days the Eternal made heaven and earth, and on the seventh day He ceased from work and rested.Exodus 31:17
The word “rested” in original Hebrew is nofash—a linguistic cognate with nefesh. This meaning of the word nefesh implies that the soul comes to rest in the human body. In the glassblower analogy, this nefesh corresponds with the final stage where the air exhaled by the glassblower comes to rest in the molten glass, forming a vessel. In Genesis 2:7, the breath exhaled by G‑d comes to rest in the body of a man who becomes the living soul.
As we see in physics, all bodies eventually come to rest (when they reach the state in which they have minimum energy). Thus, the state of rest may be allegorically viewed as the state of having reached a final destination, the “goal.” Accordingly, we can say that the body is the ultimate destination of nefesh—because this most basic level of the soul is destined to be vested in the body.
The word nefesh is also etymologically related to breath—hence the translation into Greek as psyche, meaning “breath.” Indeed, breath is the most vital function of a living body. In Hebrew and other closely related Semitic languages, the word nefesh means “neck,” “throat,” “appetite,” or “desire.”
In Jewish ritual law, halakhah, breath is identified with life. So long as a human being breathes, the body is considered alive. Conversely, the cessation of breath is viewed as the departure of the soul from the body, the moment at which it is no longer considered alive. Viewed from the stance of Kabbalah mysticism, breathing is seen as the reflection of the universal cycle of ratzo v’shov (“running and returning”; see more on this below, in the section on neshamah). The ratzo v’shov is viewed as the breath of the universe or the universal symphony of life. Once breathing stops, the music of life stops, too.
It is easy to see how the meanings of nefesh as a throat or a breath are related. Breath comes from the neck and throat. So, too, the appetite and desire for food and drink that give sustenance to the body are associated with the throat, which swallows the food or drink. Thus, nefesh takes on the meaning of breath and the natural instincts that sustain life.
Anatomically, nefesh is seen as primarily expressed in the blood. Hence the biblical prohibition against eating the blood of animals. Physiologically, nefesh is associated with motor functions, as mentioned above. But each of the five levels of the soul also has its correlate in consciousness. Nefesh correlates with the existential feeling of being alive. This subjective and ineffable feeling is called qualia. The so-called hard problem of consciousness is that it is impossible to imagine how subjective qualia can emerge from the physical brain. As the philosopher of mind David Chalmers writes:
[E]ven when we have explained the performance of all the cognitive and behavioral functions in the vicinity of experience—perceptual discrimination, categorization, internal access, verbal report—there may still remain a further unanswered question: Why is the performance of these functions accompanied by experience?
I propose an answer rooted in the metaphysics of the soul. It is not the mind but the soul that experiences qualia. The hard problem of consciousness makes the soul hypothesis a necessity—we cannot explain this problem without positing that something other than the mind—the soul—experiences qualia. Let us recall that quale is a subjective experience. However, any subjective experience requires a subject that experiences it. I think it is the soul that is the subject, which can experience a subjective experience. Specifically, it is suggested that the subjective feeling of simply being alive is experienced by nefesh.
In Kabbalah, nefesh is a feminine soul corresponding to the sefirah of Malchut and the partzuf of Nukvah. It is rooted in the spiritual strata of the world of Asiyah (the world of Action). It is, therefore, not surprising that nefesh is seen as responsible for the motor functions—the action of the body.
Ru’ach. Ru’ach (pronounced roo-ahkh) means “spirit.” The literal meaning of this word is “wind.” The Greek equivalent of this Hebrew word is pneuma (Latin spiritus), connoting the soul, but is literally translated as “breath,” “blow,” or “wind.” The connection between “spirit” and “wind” is that both are ethereal. Moreover, spirit is the basic entity in the spiritual (nonmaterial) domain. This is why the nonmaterial domain is called spiritual. As discussed above, the primary difference between the nonmaterial and material domains is space. All material objects exist in three-dimensional material space. Conversely, an entity existing outside of material space is not material. For example, thought is not material because it does not exist in space; it exists in the mind. Love is not material either, for the same reason—it exists outside the limitations of space. Spiritual entities exist outside our three-dimensional material space. They may exist in some abstract conceptual space, but this would not be our material space. The wind is something familiar to us that, albeit material, appears to be not limited by space. It has no fixed shape; it occupies no particular place; it has no fixed volume or even density; it freely moves in space from place to place. Today, of course, we know that wind is a collection of air molecules that move in space more or less together. However, the wind is an excellent metaphor for the spirit because it, at least, appears to resemble some of the properties of the nonmaterial entity we call “spirit.”
Not everyone merits having the level of ru’ach revealed. The Zohar states that a person is first given a nefesh, and “if he merits more, he is given a ru’ach,” etc. The Arizal also quotes this Zohar.
This second level of the soul is responsible for emotions. Emotions, like anger or fear, tend to rise quickly as a gust of wind. The world of emotions is a turbulent world where emotions rise and dissipate, and conflicting feelings create anxiety and emotional instability. Turbulent winds behave similarly, which is another reason for which the word for both “spirit” and “wind” is the same in Hebrew—a very parsimonious language where the same words are used to connote similar ideas. Last but not least, just as the wind moves sailboats to their destination, so too, emotions are the biggest motivators in human (and animal) behavior.
On top of “spirit” and “wind,” ru’ach also means “breath.” The connection is apparent—rapid air movement through the nose and trachea during breathing can be seen as wind, defined as rapid air movement. It is no coincidence that in English, the trachea is also called the windpipe.
Just as the pipe in the hands of the glassblower connect the artisan with the vessel he is fashioning, so too ru’ach is the connector between the Creator and His creatures, whom He fashions and enlivens, between the lower level of the soul meshed with the material body and the higher levels that are purely spiritual and unreachable by coarse materiality. Not coincidentally, in the parallel between the levels of the soul and the letters of the Tetragrammaton, ru’ach is parallel to the letter waw, which always symbolizes a connection.
Anatomically, it is thought that ru’ach primarily expresses itself in the heart. Physiologically, ru’ach corresponds to the autonomous (specifically, sympathetic and parasympathetic) nervous system. On the level of consciousness, ru’ach corresponds with emotions. Emotions are experienced as qualia. As we discussed above, it is impossible to imagine how the ineffable and subjective experiences we call qualia can emerge from the material brain (“the hard problem of consciousness”). Once again, the metaphysics of the soul may come to the rescue. As mentioned above, I believe that the soul, not the mind, experiences qualia. Specifically, in Jewish tradition, emotional experiences are felt by ru’ach.
In Kabbalah, ru’ach is the masculine soul corresponding to six midot (the low sefirot—Chesed, Gevurah, Tiferet, Netzach, Hod, Yesod) and the partzuf of Ze’ir Anpin (Z”A, the “Small Face,” the “Small Countenance,” or Microprosopus). Ru’ach is rooted in the world of Yetzirah (the world of Formation). Since Yetzirah is the world where partzuf Ze’ir Anpin (Z”A) “nests,” and the Z”A is made of six emotional traits (midot) of Atzilut, it is not surprising the ru’ach is seen as responsible for emotional attributes of the person.
Neshamah. Neshamah also means soul or, literally, “breath” (neshimah). As we see in the story about the creation of Adam (Genesis 2:7), G‑d breathed into him the breath [neshamah] of life. Chasidic philosophy explains the connection between the soul and breath as follows. When administering CPR using mouth-to-mouth resuscitation, the person doing so forces air into the lungs of the victim by exhaling into the victim’s mouth. By analogy, metaphorically speaking, to breathe life—that is, a soul—into Adam, G‑d had to “exhale” from within Himself. This analogy helps us to understand that a soul is a piece of G‑d, which He exhaled from Himself into the first human being.
There is another important connection between the breath and the soul. Note that all levels of the soul discussed so far—nefesh, ru’ach, and neshamah—share the common meaning of “breath.” Breathing is a cyclical process comprising two actions—inhaling and exhaling. The soul is never still. When in the human body, it wants instead to be with G‑d—its source. This creates a suicidal tendency in the soul: its wish to expire so as to merge with the divine. However, as soon as it soars upward, getting closer to G‑d, it regains the clarity of vision and recalls that it was sent down to earth for a purpose, and that its place is in the body. So, the soul dutifully returns to the body, where, once again being distant from G‑d, it again feels lovesick and longs to merge with its source, only to repeat this cycle again and again.
In Kabbalah, this cycle is called ratzo v’shov—running and returning. Ratzo (“running”) is a state of longing to cleave to G‑d, to transcend the material limitations of the body, to run toward G‑d and merge with the divine. Shov (“returning”) is the return to material existence in order to fulfill the soul’s mission of elevating the body. If ratzo is a state of religious ecstasy, shov is a state of sober realization by the soul of its mission below. This ratzo-v’shov (running and returning) cycle repeats itself alongside the cycle of breathing so long as the person is alive. The ratzo-v’shov cycle comes from the vision of Ezekiel—Ma’aseh Merkavah (“Work of Chariot”), where the prophet saw angels running and returning.
And the Chayot (angels, lit. living beings) were running and returning…Ezekiel 1:14
The cycle of running and returning or ratzo v’shov is the secret of time and the main principle of the spiritual dynamics that permeate all of creation.
Anatomically, neshamah expresses itself primarily in the brain. Physiologically, the third level of the soul is associated with the person’s cognitive faculties, specifically with cognition, self-cognition, and metacognition. This meaning is derived from the biblical verse in Job:
Indeed, it is a spirit (ru’ach) in man, and the soul (v’nishmat) of the Almighty permits them to understand.Job 32:8
On the level of consciousness, neshamah correlates with consciousness itself. The difficulty of explaining consciousness as a phenomenon arising out of the material brain is another aspect of the difficult problem of consciousness. Although it is entirely possible—even inevitable—to create artificial intelligence and thinking machines that match the intellectual capacity of the human mind, it is utterly impossible to create an artificial consciousness, to create conscious robots. Consciousness necessarily incorporates the subjective notion of self. Self, on the other hand, is the subject that experiences the subjective experiences we call qualia, which are undefinable and ineffable. From the point of view of metaphysics of the soul, it is the soul, not the mind, that is the ultimate self that feels the qualia. There can never be an artificial self, because there can never be an artificial soul.
In Kabbalah, neshamah is a female soul associated with the sefirah of Binahand with the partzuf of Ima (the “Supernal Mother”). Neshamah is rooted in the world of Beriyah (the world of Creation). Partzuf of Ima, which is Binah—intellect—nests in the world of Beriyah. Therefore, it is not coincidental that neshamah corresponds to the intellectual faculties.
The triad of nefesh, ru’ach, and neshamah comprise the three intrinsic levels of the soul that are vested in the body. That is why they are called pnimim (“internals” or “inner” [souls]).
A loose parallel may be drawn between the NaRaN on the one hand, and the tripartite theory of the soul in the classical philosophy of Plato and Aristotle and in Sigmund Freud’s structural model of the psyche, on the other hand:
|Nefesh||Eros or epithumetikon||Vegetable soul||Id|
|Ruach||Thymos or thumoeides||Sensitive soul||Ego|
|Neshamah||Logos or logisticon||Rational soul||Super-ego|
Chayah. The next two levels of the soul, chayah and yechidah, are very different from the first three, which are, as noted above, vested within the body. Chayah and yechidah are not in the body but rather surround and envelop it from outside, which is why they are called makifim (“envelopments”) or crowns (in that a crown sits on the head, transcending it). Similarly, these two higher levels transcend the body. They rarely manifest in the body, except on Yom Kippur and other rare occasions. They will be internalized in the Hereafter, that is, chayah and yechidah will be able to interact with—and will be revealed in —the body just as the first three levels of the soul—nefesh, ru’ach, and neshamah.
Chayah literally means “life” and is usually translated as “life force” or “living essence.” There is no anatomical correlate for chayah, because it is not vested in the body. Chayah is a close makif; that is, it envelops the body as closely as a well-tailored bespoke garment does. Physiologically, chayah is associated with volition. On the level of consciousness, it is associated with willpower (ratzon), which is the external aspect of the sefirah of Tiferet and the partzuf of Arich Anpin (“Long Face”/“Extended Countenance,” or Macroprosopus). In another context, it is also considered an intellectual soul and is associated with the sefirah of Chokhmah. Chayah is rooted in the world of Atzilut.
Once again, the metaphysics of the soul helps to resolve a conundrum. Many contemporary philosophers and neuroscientists deny the existence of freedom of choice, insisting that our choices are determined by subconscious neuronal activity. This position contradicts human experience. We subjectively feel as if we are free agents with volition and freedom of choice. The metaphysics of the soul supports this intuition by asserting that the level of soul called chayah is the source of our volition.
Yechidah. The word yechidah comes from yachid, meaning “the only one,” “unique,” or “singular.” This highest “level” of the soul is the essence of the soul. Yechidah is usually translated as “unique soul” or “unique essence.” I prefer to translate it literally as “singularity.” In physics, a singularity is a point where material parameters—such as the density of matter, or the power of gravitational forces inside a black hole or at the first instant of the Big Bang—become infinite. On a spiritual level, yechidah represents the godly spark—the infinite within the human soul. Thus, it is appropriate to call it a singularity in the soul—the point where we connect with the Infinite. The word yachid also refers to G‑d, who is the only one. Thus, yechidah may be understood as the godly essence of the soul that is always united with its Creator. Accordingly, yechidah is sometimes translated as “oneness.”
As with chayah, there is no anatomical correlate of yechidah, because these levels of the soul are not vested in the body. And, just like chayah, yechidah is not within the body but surrounds it like an aura. Thus, we find in Etz Chayim:
You should know that the three levels of soul—nefesh, ru’ach, and neshamah—are enclosed within vessels, which are the body. The “soul of soul” [neshamah d’neshamah], however, cannot be confined within the human body, but remains outside in the form of surrounding light.
However, unlike chayah, which is a close makif, yechidah is a remote makif; that is, it loosely envelops the body like a cape.
We must be careful when thinking about souls. When speaking of the soul being “in the body” or “surrounding” the body, we do not mean these phrases in a literal sense. The body of a person, which has a definite location in space and a definite shape, does not define the soul’s location or shape, because location and shape are not applicable to any nonmaterial entity such as a soul. Rather, these colloquial expressions need to be understood metaphorically. When we say that the first three levels of the soul—nefesh, ru’ach, and neshamah—are invested in the body, we mean that these levels interact in a back-and-forth way: the soul affects and is affected by the body. In the language of philosophy, these levels of the soul are immanent. The soul illuminates and enlivens the body, and, at the same time, the soul feels our pain.
When we say that the two higher levels of the soul—chayah and yechidah—surround the body, we mean that these levels are so transcendent that they are not commensurate with the body’s ability to absorb their light. They do not interact with the body directly but rather indirectly: directing the body by volition rooted in chayah and receiving feedback from the body in the form of pleasure.
Physiologically, yechidah is associated with pleasure and delight. While all qualia are subjective, the feeling of pleasure is perhaps the most subjective feeling of all. This quale is unique to each person. Robots, no matter how smart, can never feel pleasure. That is why they can never become conscious like humans. Whereas artificial intelligence (AI) is by now an everyday reality, artificial consciousness remains an impossibility.
In Kabbalah, chayah is and yechidah are both rooted in the sefirah of Keter: chayah is associated with the externalities of Keter, which is the partzuf of Arich Anpin (”extended countenance,“ Macroprosopus), whereas yechidah is associated with the inner aspect of Keter and with the partzuf Atik Yomin (the “Ancient of Days”). Arich Anpin is associated with will (ratzon) and Atik Yomin is associated with pleasure (ta’anug). It is not surprising, therefore, that chayah is associated with volition, and yechidah is associated with pleasure.
While it is possible to get an impression that these five levels of the soul are separate souls, in reality, they are five levels of one soul. We see this directly in the midrash that is the primary source for these five levels of the soul: “By five names is the soul called: nefesh, ru’ach, neshamah, chayah, yechidah.” It is clear from this midrash that these are fine names—or five levels—of the same soul. The Arizal states so explicitly with respect to the first three levels:
As you already know, these three [nefesh, ru’ach, and neshamah] are considered one collective entity.
The proof for this perhaps can be found in the verse:
Then the Eternal G‑d formed man of the dust of the ground, and breathed into his nostrils the breath of life (nishmat chayim); and man became a living soul (l’nefesh chayah).Genesis 2:7
A careful analysis of this verse reveals that G‑d breathed into Adam a living soul (nishmat chayim) referred to in this verse as neshamah, but Adam became a living soul (l’nefesh chayah) referred to as nefesh. Were neshamah and nefesh two different souls, it would have been impossible for Adam to receive one soul, neshamah, only to end up with another soul, nefesh. Since this cannot be, we must interpret this verse to mean that nefesh and neshamah are merely two levels of the same soul. Indeed, the Chasidic philosophy of Chabad explains that, whereas Adam was given the higher level of soul, neshamah, at the moment of his “birth,” only the lower level, nefesh, was revealed, as is the case with a newborn child.
In Kabbalah, the five levels of the soul are seen as rooted in the sefirot as follows:
|Level of the Soul||Corresponding Sefirah/Sefirot|
|ru’ach||Six midot: Chesed, Gevurah, Tiferet, Netzach, Hod, Yesod|
The five levels of the soul are also parallel to five partzufim (divine visages), as follows:
|Level of the Soul||Corresponding Partzuf|
|chayah||Arich Anpin or Aba|
Moreover, these partzufim themselves have five levels named nefesh, ru’ach, neshamah, chayah, and yechidah. According to the Arizal:
In every place in every world the partzufim in that world all have five parts: nefesh, ru’ach, and neshamah—the lower, middle, and upper levels of the soul—chayah, and yechidah. These are doubled, since there are five inner aspects and five surrounding aspects. Each one of these also has two other aspects: The greater lights are in the front and the lesser lights are in the back. All of this is true both for the lights and for the aspect of vessels, since vessels also have both a front and a back.
As each of these partzufim nests in one of the spiritual worlds, each level of the soul corresponds to a world, as follows:
|Level of the Soul||World|
As discussed above (see Table 1), ultimately, these correspondences come from the five elements of the Tetragrammaton. Putting it all together, we have:
|Level of the Soul||Letter of the Tetragrammaton||Sefirah||Partzuf||World|
|yechidah||kotz—the apex of the yud||Keter||Atik Yomin||Adam Kadmon|
|ru’ach||waw||Six midot: Chesed, Gevurah, Tiferet, Netzach, Hod, Yesod||Ze’ir Anpin||Yetzirah|
As if five levels of the soul weren’t enough, each of the five levels comprises all the others. Thus, besides five levels—nefesh, ru’ach, neshamah, chayah, and yechidah—there are many more levels. Twenty-five more, to be exact:
nefesh of nefesh, ru’ach of nefesh, neshamah of nefesh, chayah of nefesh, yechidah of nefesh;
nefesh of ru’ach, ru’ach of ru’ach, neshamah of ru’ach, chayah of ru’ach, yechidah of ru’ach;
nefesh of neshamah, ru’ach of neshamah, neshamah of neshamah, chayah of neshamah, yechidah of neshamah;
nefesh of chayah, ru’ach of chayah, neshamah of chayah, chayah of chayah, yechidah of chayah; and nefesh of yechidah, ru’ach of yechidah, neshamah of yechidah, chayah of yechidah, yechidah of yechidah.
It is interesting to note that, according to the esoteric wisdom of Kabbalah, not only do humans and animals have souls, but angels are also said to have a soul and a “body.”
Having considered different levels of the soul, next we will examine different types of souls, such as Nefesh Elokit (the godly soul), Nefesh HaBahamit (the animal soul), Nefesh HaSichlit (the intellectual soul), and others.
 Pronounced (and often spelled as) ru’ach.
 These three levels are not to be confused with the trichotomy found in non-Jewish sources: body (soma), soul (psyche), and spirit (pneuma). First, the trichotomy recognizes only two souls—psyche and pneuma. Second, the trichotomy assumes that these are three metaphysically different substances, whereas Judaism speaks of three (actually, five) levels of one soul. There are other principal distinctions as well.
 Genesis Rabbah 14:9.
 The Talmud states, “Five times David said: “Bless the Lord, O my soul,” each corresponding to a different stage of life” (Berachot 10a). Perhaps this may be interpreted as hinting at the five levels of the soul, mentioned in the Psalms five times. (I have not seen this in any written sources nor have I heard this from my teachers. Thus, this is merely my speculation not found in classical sources.)
 Rayah Nehemnah, Terumah.
 Etz Chayim, Gate IV, 1. See in English Rabbi Hayyim Vital, The Tree of Life: The Palace of Adam Kadmon, translated by Donald Wilder Menzi and Zwe Padeh (Northvale, NJ: Jason Aronson, 1999), pp. 118, 239. See also Rabbi Chayim Vital, Ta’amei HaMitzvot, parshat Vayikra. See Rabbi Moshe Wisnefsky, Apples from the Orchard: Mystical Insights on the Weekly Torah Portion (Malibu, CA: Thirty Seven Books, 2008), pp. 25, 522, 857.
 Geneses Rabbah 14:7; Midrash Tehilim 2:11; Sanhedrin 91a, Rashi on Chagigah, 12b; Etz Chaim 5:5. See in English Rabbi Aryeh Kaplan, Inner Space, Introduction to Kabbalah, Meditation and Prophecy, p. 17. (See further sources there.)
 Pronounced vav. The letter waw is often alternatively spelled vav, in which case the Tetragrammaton is transliterated into English letters as Y-H-V-H.
 b’nafsho literally means “with the soul thereof.” The three-letter root of this word is NFSh (nun–peh–shin)—the same as in nefesh.
 How this interaction between physical and nonphysical works is the critical question, which must be addressed by any theory of the soul. We will have more to say on this question later.
 Some old translations of the Bible, such JPS, translate b’nafsho as “with the life thereof,” equating this basic level of the soul with the life itself.
 In some context, the word nefesh can mean “life.”
 Nefesh approximately corresponds to the vegetable soul as defined by Aristotle, with some important differences: whereas the Aristotelian vegetable soul is corporeal and mortal, nefesh is incorporeal and immortal.
 The word nefesh and its cognates have similar meanings in many Semitic languages. Thus, in Aramaic and Syriac, the words nefash and nafsho mean “the breath of life,” soul, spirit, living creature. In Akkadian, napishtu means “life,” “living creature,” a “person,” or “to get breath.” In Ancient Greek, the equivalent word is psyche, meaning “breath,” “life,” “spirit,” “soul.” In Latin, spiritus has the same meaning as the Greek psyche.
 See also, “Six days thou shalt do thy work, but on the seventh day thou shalt rest; that thine ox and thine ass may have rest, and the son of thy handmaid, and the stranger, may be refreshed” (Exodus 23:12). The word “refreshed” (or rested) in Hebrew is vainafesh—cognate with nefesh.
 Consider the verse from Jonah: “The waters compassed me about, up to the neck; the deep was round about me; the weeds were wrapped about my head” (Jonah 2:6). The word “neck” in the original Hebrew is nefesh, which is why in some translations it is rendered in English as “soul.” Or consider the following verses from Psalms: “Save me, O G‑d; for the waters are come in up to the neck” (Psalms 69:2) and “His feet they hurt with fetters, his neck was laid in iron” (Psalms 105:18). In both verses, nefesh means “neck.”
 Consider this Torah verse: “And I will set My tabernacle among you, and My soul [lit. “throat”] shall not abhor you” (Leviticus 26:11). In this verse, the literal translation of the word nefesh is “throat” (meaning, “My throat will not vomit you out.” Also, “And the people spoke against G‑d, and against Moses: “Wherefore have ye brought us up out of Egypt to die in the wilderness? for there is no bread, and there is no water; and our soul (lit. “throat”) loatheth this light bread” (Numbers 21:5). In all these verses the Hebrew word nefesh literally means “throat.”
 See the verse, “Therefore the Sheol hath enlarged her desire, and opened her mouth without measure; and down goeth their glory, and their tumult, and their uproar, and he that rejoiceth among them.” Here the Hebrew word nafsho that is a cognate with nefesh means “desire” or “appetite.”
 This definition of life has profound ramifications for medical ethics in deciding when it is permissible to turn off life support.
 See, for example, “All the days that he consecrateth himself unto the Eternal he shall not come near to a dead body [nefesh]” (Numbers 6:6). When used with a qualifier (such as chayah, meaning “live,” or met, meaning “dead”), the word nefesh means “body”—a live body or a dead body, depending on the qualifier. In this verse, nefesh met means a dead body.
 See, for example, “And the king of Sodom said unto Abram: “Give me the persons [ha-nefesh], and take the goods to thyself” (Genesis 14:21); “And if a person [v’nefesh] sins…” (Leviticus 5:1); “that the manslayer that killeth any person [nefesh] through error and unawares may flee thither; and they shall be unto you for a refuge from the avenger of blood” (Joshua 20:3).
 Some examples of this prohibition: “But, flesh with its [animal’s] soul, its blood, you shall not eat” (Genesis 9:4); “And if anyone of the house of Israel or of the strangers who reside among them partakes of any blood, I will set My face against the person who partakes of the blood, and I will cut him off from among his kin. For the soul (nefesh) of the flesh is in the blood, and I have assigned it to you for making expiation for your lives upon the altar; it is the blood, as life, that effects expiation. Therefore I say to the Israelite people: No person among you shall partake of blood, nor shall the stranger who resides among you partake of blood. . . . For the life (nefesh) of all flesh—its blood is its soul (b’nafshoi). Therefore I say to the Israelite people: You shall not partake of the blood of any flesh, for the soul (nefesh) of all flesh is its blood. Anyone who partakes of it shall be cut off” (Leviticus 17:10-12, 14); and “[M]ake sure that you do not partake of the blood; for the blood is the soul (ha-nefesh), and you must not consume the soul (ha–nefesh) with the flesh” (Deuteronomy 12:23).
 In philosophy of mind, qualia is the plural of quale, which is defined as an instant of subjective conscious experience. The word quale comes from Latin quālis, which means “of what sort” or “of what kind,” as in “What does it feel like to experience this taste now?” One of the simplest definitions of qualia is the “‘what it is like’ character of mental states.” Australian philosopher Frank Jackson defined qualia as “certain features of the bodily sensations especially, but also of certain perceptual experiences, which no amount of purely physical information includes.” See Jackson (1982), “Epiphenomenal Qualia,” Philosophical Quarterly, 32 (127): 127–136, doi:10.2307/2960077. Four properties are commonly ascribed to qualia: the qualities of being ineffable, intrinsic, private, and directly apprehensible by consciousness.
 The hard problem of consciousness, a.k.a. the hard problem of philosophy, is the problem of explaining why and how we have qualia. This contrasts with “easy” problems whose solution requires the identification of the neural mechanism responsible for particular functions. According to the philosopher David Chalmers, even after we solve all such problems about the brain and experience, the hard problem still persists. See Chalmers, “Facing Up to the Problem of Consciousness,” Journal of Consciousness Studies, 1995, 2 (3): 200–219.
 Chalmers, “Facing Up to the Problem of Consciousness,” p. 203.
 In 1990, Francis Crick (a co-discoverer of the double helix of DNA) and neuroscientist Christoff Koch suggested that neural correlates of mental states are neuronal oscillations. See Crick and Koch, “Towards a Neurobiological Theory of Consciousness,” Seminars in Neuroscience, 1990, 2, 263–275. In my recent paper, I argue that brain states, having brain waves as their neural correlates, can be “transplanted” from one person to another and thus are not subjective. See Poltorak, “Replicating Cortical Signatures May Open the Possibility for ‘Transplanting’ Brain States via Brain Entrainment,” Frontiers of Human Neuroscience, 22 September 2021, https://doi.org/10.3389/fnhum.2021.710003. That means that the subjective experience of brain states lies outside the neuronal oscillations and resulting brain waves that is outside brain activity. Pain, for example, is a brain state, which is expressed in neuronal oscillations. However, the subjective experience of pain is something entirely different and requires other than a brain to experience this brain state. I would argue that the soul is the subject of any subjective experience that experiences a brain state.
 Kabbalah speaks of four worlds in the ontological chain of creation: Atzilut (the world of “Emanation”), Beriyah (the world of “Creation”), Yetzirah (the world of “Formation”), and Asiyah (the world of “Action”). The last world of Asiyah has two strata, Olam HaAsiyah Ruchni (the Spiritual World of Action) and Olam HaAsiyah Gashmi (the Material World of Action—the world we inhabit).
 Consider the following biblical verses: “Now the earth was unformed and void, and darkness was upon the face of the deep; and the spirit of G‑d hovered over the face of the waters” (Genesis 1:2); “And the Eternal said: ‘My spirit shall not abide in man for ever, for that he also is flesh; therefore shall his days be a hundred and twenty years’” (Genesis 6:3); “And I have filled him with the spirit of G‑d, in wisdom, and in understanding, and in knowledge, and in all manner of workmanship” (Exodus 31:3); “Let the Eternal, the G‑d of the spirits of all flesh, set a man over the congregation” (Numbers 27:16); “And the Eternal said unto Moses: ‘Take thee Joshua the son of Nun, a man in whom is spirit, and lay thy hand upon him” (Numbers 27:16); “And Joshua the son of Nun was full of the spirit of wisdom; for Moses had laid his hands upon him; and the children of Israel hearkened unto him, and did as the Eternal commanded Moses” (Deuteronomy 34:9). In all these verses, the word ru’ach has the meaning of “spirit.”
 Consider the following biblical verses: “And G‑d remembered Noah, and every living thing, and all the cattle that were with him in the ark; and G‑d made a wind to pass over the earth, and the waters assuaged” (Genesis 8:1); “And Moses stretched forth his rod over the land of Egypt, and the Eternal brought an east wind upon the land all that day, and all the night; and when it was morning, the east wind brought the locusts” (Exodus 10:13); “And the Eternal turned an exceeding strong west wind, which took up the locusts, and drove them into the Red Sea; there remained not one locust in all the border of Egypt” (Exodus 10:19); “And a man shall be as in a hiding-place from the wind” (Isaiah 32:2); “And I looked, and, behold, a stormy wind came out of the north” (Ezekiel 1:4); “Daniel spoke and said: I saw in my vision by night, and, behold, the four winds of the heaven broke forth upon the great sea” (Daniel 7:2). “The wind goeth toward the south, and turneth about unto the north; it turneth about continually in its circuit, and the wind returneth again to its circuits” (Ecclesiastes 1:6); “He that observeth the wind shall not sow; and he that regardeth the clouds shall not reap” (Ecclesiastes 11:4); “As thou knowest not what is the way of the wind, nor how the bones do grow in the womb of her that is with child; even so thou knowest not the work of G‑d who doeth all things” (Ecclesiastes 11:5). In all these and many other biblical verses, the word ru’ach has the meaning of “wind.” The word ru’ach has a similar meaning in other Semitic languages. In Syriac, rach means “he breathed,” and rucha means air or wind. In Aramaic, rucha means “wind,” “breath” or “spirit.” In Ugarit, the two-letter root rḥ means wind.
 Indeed, the word revach that shares the root RVCh with ru’ach means “space.” See, for example, “Pass over before me, and put a space [v’revach] betwixt drove and drove.” (Genesis 32:17).
 Zohar II, 94b.
 Shaar HaMitzvot, parshat VaEtchanan.
 Ru’ach approximately corresponds to the sensitive soul as defined by Aristotle, with some important differences: whereas the Aristotelian sensitive soul is corporeal and mortal, ru’ach is incorporeal and immortal.
 In Hebrew grammar, the prefix waw means “and” and connects two words. For example, aba v’ima means “father and mother,” joining the two together.
 In Kabbalah, partzufim are constructed from the sefirot of Atzilut (world of “Emanation”). However, each partzuf primarily expresses itself—“nests”—in each of four worlds of Seder Hishtalshelut (chain of ontological unfolding of Creation in four worlds): partzuf Aba nests in Atzilut, partzuf Ima nests in Beriyah, partzuf Ze’ir Anpin (Z”A) nests in Yetzirah, and partzuf Nukvah nests in Asiyah.
 This word is derived from the root neshem, that is, “to breathe.” In most Semitic languages the cognates of neshem means “to breathe.” For example, in Syriac and Aramaic, nesham means “he breathed.”
 Man d’nafach mi’tochei nafach (“He who breathed, from within Himself He breathed”). See Rabbi Schneur Zalman, Tanya 2, quoting the Zohar.
 Needless to say the such words as “exhale” or “piece” need to be understood not literally—incorporeal G‑d obviously doesn’t have lungs to exhale nor does He have any “pieces”—these are purely allegorical constructs used to illustrate lofty spiritual concepts that are difficult to express in human language.
 Kabbalah and Chasidic literature this suicidal tendency of the soul is called k’lot hanefesh. See the story of Nadav and Avihu—Aaron’s two oldest sons—who died in k’lot hanefesh being consumed by the fire that came from G‑d (Leviticus 10).
 As we explained above with respect to nefesh, the body is the destination, the “goal” of the soul (at least on the level of nefesh), which is destined to be vested in the body to elevate it.
 V’nishmat is a grammatical form of neshamah and literally means “and the breath of” or “and the soul of.”
 Neshamah approximately corresponds to the rational soul as defined by Aristotle, with some important differences: whereas the Aristotelian rational soul is mortal (albeit incorporeal), neshamah is immortal.
 Tanya, Iggeret HaKodesh, Epistle 15.
 The triad of nefesh, ru’ach, and neshamah very roughly corresponds to the Aristotelian triad of souls—the vegetable soul, the sensitive soul, and the rational soul. Of these three, Aristotle thought that the vegetable soul and the sensitive soul were corporeal, and only the rational soul was incorporeal. He also thought that all these souls were mortal and died together with the body. See Aristotle, De Anima. Of course, nefesh, ru’ach, and neshamah are incorporeal and believed to be immortal. There are other technical differences that are not important for this overview.
 Exodus Rabbah 3:1 and 45:5; Midrash Tanchumah on Shemot 19.
 See Tanya, Iggeret HaKodesh, Epistle 15, which reads, “Chokhmah gives life” (Ecclesiastes 7:12).
 Although, yechidah is often characterized as the “fifth level” of the godly soul, strictly speaking, it is not a level but rather the essence of the soul. If it was a level, it would only relate to the previous levels as something being higher than the levels below it. However, as the essence, it is present within each level of the godly soul. See, Rabbi Menachem M. Schneerson, “On the Essence of Chasidus,” Kehot.
 Rabbi Aryeh Kaplan, Inner Space, Introduction to Kabbalah, Meditation and Prophecy, p. 20.
 See for example the prayer Baruch She’amar, which refers to G‑d as Yachid, Chei Ha’olamim, Melech (“the Only One, Life of the Worlds, King”).
 In most places, the Zohar did not differentiate between chayah and yechidah, instead, combining them under one rubric, neshamah d’neshamah (the “soul of souls”). However, Tikunei Zohar and, later, the Eitz Chaim appears to use the term neshamah d’neshamah to connote chayah, while treating yechidah separately.
 Eitz Chaim, Gate 4. Here we use the English translation from Rabbi Hayyim Vital, The Tree of Life: The Palace of Adam Kadmon, p. 120.
 The argument can be made that nefesh, ru’ach, neshamah, chayah, and yechidah are distinct souls and distinct metaphysical entities based on the Kabbalistic doctrine of transmigration of souls (gilgul), or metempsychosis. There are a number of references in the writings of the Arizal discussing how nefesh, ru’ach, or neshamah of the same individual reincarnated in different people. The counterargument is that, as a nonphysical entity, the soul occupies no particular space. The same soul can illuminate different bodies without being splintered into different souls. The fact that different aspects of the same soul manifest themselves more prominently in a particular person is not proof that it is a different soul.
 According to the Arizal, five aspects of animal sacrifice (korban) correspond (and are intended to elevate and atone for) the five levels of the soul: the salt atones for nefesh, oil and wine atone for ru’ach, the animal itself atones for neshamah, the verbal confession of the person bringing the offering atones for chayah, and the intention (kavanah) of the priest corresponds with yechidah (Taamei HaMitzvot, Parsha Vayikra). See in English Rabbi Moshe Wisnefsky, Apples from the Orchard: Mystical Insights on the Weekly Torah Portion, p. 522.
 Genesis Rabbah 14:9.
 Sefer HaLikutim, Parshat Vayechi; see also Rabbi Moshe Wisnefsky, Apples from the Orchard: Mystical Insights on the Weekly Torah Portion, p. 242.
 Partzufim (divine visages) are dynamic configurations of interincluded sefirot in the Universe of Tikun. For example, Partzuf Aba (“Father”) is the sefirah of Chokhmah as it includes all ten sefirot within itself. Similarly, Partzuf Ima (“Mother”) is the sefirah of Binah as it includes all ten sefirot within itself, etc.
 Rabbi Hayyim Vital, The Tree of Life, The Palace of Adam Kadmon, p. 239. Furthermore, according to Eitz Chaim, these five levels are doubled, because the soul has internal and external aspects, and further doubled because each has “front” and “back” aspects. Eitz Chaim, Gate 4, 2. See, in English, Rabbi Hayyim Vital, The Tree of Life, The Palace of Adam Kadmon, p. 239.
 Zohar II, 94b.
 This interinclusion should not come as a surprise. Such fractal self-similar structures are typical. We find first it in the sefirot, where each of the ten sefirot includes all others: Chokhmah of Chokhmah, Binah of Chokhmah, etc. We also find it in the ontological chain of created worlds: Atzilut of Atzilut, Beriyah of Atzilut, etc.
 Tanya, Likutei Amarim 40, Iggeret HaKodesh 20.