Nefesh — The Vital Animating Soul
The lowest and most basic level of soul, the animating life-force bound to the body that a person shares in some form even with animals.
Nefesh is the soul-level most closely tied to physical existence — associated in classical sources with the blood, since Torah describes the blood itself as carrying nefesh, and treated as the seat of instinct, appetite, and basic bodily vitality rather than moral or intellectual life. Genesis's account of Adam's creation describes God forming the body and breathing life into it so that man became a living soul, the verse Kabbalists point to as this level's textual anchor. Because Nefesh is the soul-level every living creature possesses in some form, Kabbalists treat it as the necessary starting point rather than the goal: it must be present and functioning before Ruach or Neshamah can develop on top of it, much as a foundation must exist before a house can be built. In practical terms, Nefesh is the level engaged by physical mitzvot and bodily discipline, since it is the soul-layer most directly reachable through the body itself.
man became a living soul
Zohar