Classical kabbala identifies four levels of the soul - called Nefesh, Ruach, Neshama and Neshama L'neshama. Nefesh is the animating principle of the physical body and the senses; ruach is the force vitalizing the emotions; neshama is the vitality of intellect; and neshama l'neshama is the essence of life of the human soul. The Arizal refers to this fourth level of soul as Chaya, signifying its function as the essence of life. However, all these four aspects of the soul he regarded as mere extensions of the essence of the soul, which he called Yechida.

…Between the Creator and the created [i.e., the aspect of spirituality in general, as opposed to physical creation] there is an intermediate level, regarding which it states, "You are children of G‑d your Lord…," for our Sages have declared, "the Patriarchs are the merkava [the Divine Chariot]." The intention here is that a tiny spark of G‑dliness, drawn from the lowest level of the Creator, clothes itself in a single spark of the created in potentia, which is an extremely ethereal soul. Within this soul-spark, called Yechida, are the roots of all the other four levels of spirituality - Nefesh, Ruach, Neshama and Chaya. (Etz Chaim, shaar 42, chap 1) The soul is both part of the Creator and at the same time it is created…

In other words, the soul is both part of the Creator and at the same time it is created. Its luminous essence is "a tiny spark of G‑dliness", and the sheath in which it is clothed is a created being, albeit a spiritual being and not physical. As the soul emanates from the Ein Sof eventually to be clothed in the physical body, the soul descends via the four worlds mentioned above, leaving a root in each of the worlds1 - Chaya in the world of Atzilut, Neshama in the world of Beriya, Ruach in the world of Yetzira, and Nefesh in the spiritual dimension of Asiya. (Shaar HaGilgulim, hakdama 1) All of this is then enclothed within a physical body.

The soul enclothed within the body is a reflection of the Divine Form, called the "Tzelem", or "Tzelem Elokim". This "Tzelem Elokim" may be described as the human mold of man's physical form, linking his body and soul. This mold derives from the configuration of the sefirot, which form the structure of the worlds through which the soul descends on its journey down into the body.

At the same time that the soul's outer dimension reflects the configuration of the sefirot, the inner dimension of the soul reflects the Infinite Light that illuminates the sefirot. This reflection is called the "Demut Elokim" (literally, the "Image of G‑d"; see R. Chaim Vital's Shaarei Kedusha, part 3, ch. 5, and Likutei Torah, Shir Hashirim, Rabbi Shneur Zalman of Liadi). Thus man includes all of creation within him, from the loftiest spirituality to the most mundane physicality. (Pardes, shaar 4, ch. 10) If he purifies himself greatly, he may be able to attain the level of…Yechida, the G‑d-consciousness of the level of Adam Kadmon…

From the perspective of man's service of G‑d, these levels of soul may be described as five ascending levels of awareness of, and communion with, G‑d. Regarding these levels of soul, Zohar2 states that when a person is born, he is given a Nefesh from the world of Asiya, the lowest world, representing the greatest concealment of G‑d. If, through his divine service and proper action, he makes himself worthy, he is then given Ruach on the plane of Yetzira. With greater effort, he can earn the revelation of Neshama, paralleling the world of Beriya. If he purifies himself greatly, he may be able to attain the level of Chaya paralleling Atzilut, and even Yechida, the G‑d-consciousness of the level of Adam Kadmon and beyond. ("Beyond," because the level of soul called yechida, in essence, transcends all the worlds, since it is never separated from G‑d. It is described as being "truly part of G‑d above," the "spark of the Creator clothed within a spark of the created" described earlier. See Job 31:2 and Tanya ch. 2)

This setup puts humankind in a unique position, for through his spiritual and physical composition (soul and body) he is bound up with all levels of Creation. His actions and behavior are therefore capable of affecting all the worlds and all the sefirot. Thus, man is a microcosm of Creation, and his actions have cosmic significance. (R. Chaim Vital, Shaarei Kedusha III, 2-3) He is able to affect the balance of the universe, both spiritual and physical, by his kavanot (mystical intentions) and yichudim (unifications of the sefirot). The Arizal revealed an elaborate system of kavanot and yichudim designed to achieve this very purpose.

This ends our introduction to the basic concepts of Lurianic Kabbala.