The Sandokai is an ancient teaching poem composed by Chinese Zen master Sekito Kisen (Shitou Xiqian, 700-790). It's recited daily in Soto Zen temples throughout the world and deals with an issue of paramount importance in Zen: the relationship between the relative and absolute dimensions of reality.

In Week four we studied the lines

"Eye and sights, ear and sounds, nose and smells, tongue and tastes; Thus with each and every thing, depending on these roots, the leaves spread forth.

Trunk and branches share the essence; revered and common, each has its speech.

In the light there is darkness, but don't take it as darkness; In the dark there is light, but don't see it as light."