Among the Tree's many divisions are three triads, each composed of three Sephiroth. These triads interweave with the various worlds, and map to five souls.

The third of these triads is the bottom triad of Yetzirah: Netzach, Hod, and Yesod, referred to as the Astral or Psychological triad. This group is the part of our psyche that we think of as our subconscious.

This is also the water triad, whose ruling influence is the Moon. (A Triad's ruler, its governing influence, is the Sephirah in the middle pillar.) It has aspects of memory (Yesod, Moon) and emotion (Netzach, Venus) that are its major influences, even though it also contains the Sephirah of rationality, Hod (Mercury).

The Triads are divided from one another by veils. Above this Triad sits Paroketh, dividing it from our everyday consciousness; and below it sits the veil of the Profane, separating it from our physical body.

You can think of this triad as the passive principles. This being so, it relates in some way to the left pillar, Severity. Its base is Yesod, the Moon, which is the Treasure-House of Images, the place we keep our memories, emotions, and feelings. Of the four elements, it aligns with water (emotion) and earth (practicality).

Those of you familiar with Robert Pirsig's Metaphysics of Quality might think of this Triad as biological patterns. Emotions and sensations, our reactions to the things we experience, are common across all life: every microbe experiences something like them.