  Some commentators characterize Santayana as an epiphenomenalist, and there are some commonalities, specifically the view that spirit is not efficacious. But there also are considerable differences. Santayana does not characterize his view as one-way interactionism, primarily because he does not think of spirit as an object to be acted upon. Spirit is rather a distinguishable aspect of thought, generated in activity, and may be viewed more as a relational property. Santayana sometimes speaks of spirit and essence as supervening on material events. But lacking the distinctions of contemporary philosophy, it is difficult to characterize Santayana’s philosophy of mind accurately. His view of consciousness is more celebrational, as opposed to being a burden or eliciting action. Spirit is “precisely the voice of order in nature, the music, as full of light as of motion, of joy as of peace, that comes with an even partial and momentary perfection in some vital rhythm” (Birth of Reason, 53).