Complex sentence: In the worldview of Castaneda's teachers, reality is seen as multi-dimensional or multi-faceted which humans only perceive a portion of; the known part of reality with which humans are familiar is called the "tonal".
Split into simpler sentences: In the worldview of Castaneda's teachers, reality is seen as multi-dimensional or multi-faceted and ordinary humans only perceive a small portion of it. The known part of reality with which humans are familiar is called the "tonal".