This is rather strange. The Eve of Yom Kippur is one of the Ten Days of Repentance (Asseret Yemei Teshuvah). Shouldn’t we be busy regretting past mistakes (and, indeed, we do!) and repenting our evil ways, instead of indulging in sumptuous meals? Moreover, it’s the day before Yom Kippur—the day on which every person is judged, and everyone’s fate is sealed for the next year. In a moving prayer called Unetane Tokef, it is stated,
On Rosh Hashanah they are inscribed, and on the fast day of Yom Kippur they are sealed: How many shall pass away and how many shall be born; who shall live and who shall die….Machzor Rosh HaShanah, Unetane Tokef
Who doesn’t know this prayer? Who doesn’t cry reciting it? Most people understandably experience some anxiety before the awesome day of judgment (Yom HaDin). This is why Rosh Hashanah and Yom Kippur are together called Yomim Naroyim—the Days of Awe. So, why the festive meals on the Eve of Yom Kippur? Furthermore, the Rabbis require us to eat more than usual, which is counted to us as merit. How strange . . .
Turning to Yom Kippur itself, the Torah says:
Since the Torah mentions the ninth day (of the seventh month—the month of Tishrei—and we indeed begin the fast on the ninth until the evening of the tenth), the sages of the Talmud explain that the Eve of Yom Kippur—the ninth day of Tishrei—is also part of the atonement, even though there is no fasting. The sages say, “This teaches that one who eats and drinks on the ninth is credited as if he fasted on both the ninth and tenth” (Berachot 8b).
This is most puzzling. Why would eating on the Eve of Yom Kippur be considered fasting? And why does the Torah require us to fast on Yom Kippur in the first place? Yom Kippur is a yom tov (a holiday), and on holidays fasting is forbidden. Moreover, it is called Shabbat Shabbaton—the Sabbath of Sabbaths, the holiest day of the year. On Shabbat, it is forbidden to fast. So why do we fast on Yom Kippur? And why the additional prohibitions against other bodily pleasures—five in total—on Yom Kippur? And what does it all have to do with teshuvah(“repentance”)—the main mitzvah of the day? The answers to all these puzzling questions are found in one word—taanug or “delight.”
Kabbalah and the Chasidic philosophy of Chabad devote much attention to the concept of taanug (delight or pleasure). In Kabbalah, taanug is associated with the pnimi’ut HaKeter—the innermost aspect of the sefirah of Keter (“Crown”), which precedes the universe of Atzilut and the entire seder hishtalshelut—the ontological order of created worlds. In Lurianic Kabbalah, taanug is associated with the partzuf of Atik Yomin (“the Ancient of Days”)—the highest partzuf. The concept of taanug is so important to Kabbalah that it is sometimes used as a metaphor for Ein Sof—“the Infinite” (literally “Without End,” i.e., G‑d).
The concept of pleasure or delight is very important to the philosophy of mind as well. It is at the core of what is known as the “hard problem of philosophy.” The problem is, How can a subjective experience arise from the physical brain? No reductionist approach can account for a subjective experience. Subjective conscious experiences are called qualia (or quale in singular). An experience of pleasure is an example of qualia. While neuroscience has identified the hormone of pleasure, dopamine, it in no way explains the raw ineffable subjective feeling of pleasure. The highly subjective nature of quale in general and pleasure in particular point to the subject who experiences the experience of pleasure. Some philosophers argue that although pleasure, like other qualia, feels intensely physical and real, qualia cannot be physical and must be metaphysical. No reductionist argument can account for the subject who experiences the subjective experience.
When we talk about human pleasure (or qualia in general), we are led to conclude that a nonphysical soul is ultimately the subject of any experience. When we talk about divine pleasure, it must be the essence of G‑d that “experiences” taanug. For this reason, the revelation of the divine taanug (and the associated sefirah of Keter and partzuf of Atik Yomin) that takes place on Yom Kippur is considered the revelation of the divine essence.
Chabad philosophy distinguishes between two types of delight—taanug hapashut (simple pleasure, or pure delight) and taanug hamurkav (complex pleasure). Pleasure caused by externalities, such as food, drinks, music, ideas, etc., is considered a complex pleasure (taanug hamurkav), because the nature of the thing that causes pleasure profoundly affects the way we experience that pleasure. Different foods have different tastes. People enjoy dry wine and sweet wine with different foods and in different circumstances, because they are so different. The complex pleasure of food and drink is considered one of the lowest types of pleasure. The smell of fragrant herbs and flowers is a more refined type of complex pleasure. Delight in hearing beautiful music, in reading beautiful poetry, or in seeing a beautiful painting is a higher kind of pleasure. The delight from understanding profound ideas is higher yet. And the highest of all is the delight that comes from understanding deep insights from learning Torah, Kabbalah, or Chasidic philosophy. But these are still complex pleasures (taanug hamurkav), no matter how refined.
All of these types of delight are complex because they are greatly affected by that which gives us pleasure and delight. These pleasures have another common denominator: they fill a void, something we have missed and therefore desire. Food gives pleasure because a hungry person desires and needs food in order to exist. Once one is satiated, food stops giving pleasure. A lack of knowledge or understanding sends us on a quest to discover the missing knowledge. Once we gain that knowledge, it satisfies the need for understanding and, therefore, ceases to cause delight. And so on.
G‑d’s delight, on the other hand, is very different. G‑d is infinite and perfect; He lacks nothing. G‑d’s delight is the delight of being. G‑d delights in Himself, as it were. It is a self-referential construct. This is taanug hapashut—simple delight, which is entirely introverted and unaffected by any externalities. It is a simple pleasure of being alive, uncomplicated, and unadulterated by anything external.
Rabbi Schneur Zalman of Liadi (the Alter Rebbe) explains in his discourse on Tzimtzum that taanug hapashut is the source of life—makor chayim—and the source of forgiveness. (See maamar Lehavin Mah Shekasuv B’Otzros Chayim in Likkutei Torah, Vayikra.) It is this level, taanug hapashut, that is revealed on the day of Yom Kippur. The level that is the source of life—makor chayim—is higher than any sin, which is why forgiveness comes from that level. But it is also a level of delight.
Now we can understand why we fast on Yom Kippur. This fast is not the mortification of our bodies (as all other fasts are). Rather, on this day, the taanug hapashut (simple delight) is revealed, and it cannot be diluted and overpowered by the complex delight that comes from physical pleasures. Just as the prophets of old used to practice hitbodedut (meditation in seclusion, to quiet all senses) to hear the voice of G‑d, so too Jewish people quiet their desires and refrain from physical pleasures by fasting and otherwise, as prescribed by Jewish law, to experience taanug hapashut—the simple delight of G‑d.
Now we can also understand why eating and drinking on the Eve of Yom Kippur is counted as fasting as well. It is because both are related to delight—the leitmotiv of Yom Kippur. On the Eve of Yom Kippur, we cannot fast, so we experience complex pleasures—taanug hamurkav—from food and drinks as preparation for experiencing a higher form of delight, simple delight—taanug hapashut—on Yom Kippur itself.
This also helps us understand the connection to teshuvah—repentance. During the year, we are busy pursuing transient pleasures and instant gratifications. This pursuit pollutes and corrupts our sense of true delight; it dulls our spiritual senses. Therefore, before we can partake of G‑d’s delight, we must experience regret and divest ourselves of all those physical pleasures that overwhelmed our senses. Only then can the subtle voice of G‑d be heard, and simple delight can be experienced.
Thus, Yom Kippur is a day of pure delight. We need to cleanse ourselves of the impure delights experienced during the year so we can partake of the pure delight of godliness on Yom Kippur.
I wish you a delightful Yom Kippur and a delightful new year!
 A sefirah is a divine emanation. There are ten sefirot (pl. of sefirah): Keter, Chokhmah, Binah, Chesed, Gevurah, Tiferet, Netzach, Hod, Yesod, and Malchut.
 Keter is called “Crown” because it crowns all other sefirot as they are arranged in the Tree of Life. It is so sublime that the Zohar calls it “the most hidden of all hidden things.” The Bahir, states, “”What are the ten utterances? The first is supreme crown…” It is also the source of Thirteen Attributes of Mercy, which are revealed on Yom Kippur. Keter is hidden and unknowable, as it precedes the first intellectual emanation, Chokhmah.
 In Lurianic Kabbalah, partzuf (divine visage, countenance, or configuration) is a dynamic configuration of inter-included sefirot. Thus, for example, partzuf Aba (“Father”) is the sefirah of Chokhmah as it includes all ten sefirot.
 Atik Yomin (“the Ancient of Days”) is an appellation for G‑d (or, more precisely, a certain level of godliness) used three times in the Book Daniel. It is called “ancient” because it is the “earliest” (not in the temporal sense, but in the logical sense) source of creation that causally precedes all other levels. Atik Yomin is the inner partzuf of Keter. The external partzuf of Keter is Arich Anpin—the “Long Visage”). Atik Yomin is identified with the divine delight (taanug), whereas Arich Anpin is identified with the divine will (ratzon).
 Taanug is sometimes used as a metaphor for Ein Sof for the following reasons. As explained in footnote 4, taanug is identified with the innermost level of Keter and Atik Yomin, the uppermost partzuf. While this level is not knowable, it is the highest level we can point to as the source of creation. This is why Daniel used Atik Yomin as an appellation for G‑d. Furthermore, delight or pleasure is the most primary emotion closely identified with the essence of a being.
 Frank Jackson defines qualia as “certain features of the bodily sensations especially, but also of certain perceptual experiences, which no amount of purely physical information includes.” Frank Jackson, “Epiphenomenal Qualia,” The Philosophical Quarterly 32, no. 127 (1982): 127–136. According to Daniel Dennett, qualia are ineffable, intrinsic, private, and directly apprehensible by consciousness.
 The subjective nature of qualia was emphasized by Thomas Nagel in his frequently cited paper, “What Is It Like to Be a Bat?” in The Philosophical Review 83, no. 4 (1974): 435–450.
 This assertion is based on the inverted spectrum thought experiment, proposed by John Locke. See John Locke, “Essay Concerning Human Understanding” Oxford, UK: Oxford University Press, (1689/1975), II, xxxii, 15.
 Rabbi Schneur Zalman of Liadi, Likkutei Torah, Vayikra, maamar Lehavin Mah Shekasuv B’Otzros Chayim.
 Furthermore, the sefirah of Keter is above time. Consequently, when taanug (which is the innermost aspect of Keter) is revealed, past sins can be atoned for and errors can be rectified in the present time—on the day of Yom Kippur. That is why the sages of the Talmud stated that it is the day itself that atones for sins.