Santayana Says That We Can "Distinguish the Material of Things

Santayana says that we can "distinguish the material of things from the various forms it may successively assume; we can distinguish, also, the earlier and the later impressions made by the same object; and we can ascertain the coexistence of one impression with another, or with the memory of others. But aesthetic feeling itself has _________, and this physiology of its causes is not a description of its proper nature."

A) regulation
B) temporality
C) a heart
D) no parts