I'm trying to understand the book's philosophy. How does it define birth and death, and why are saints like Baba considered different?

The text provides a clear philosophical distinction between ordinary existence and the state of enlightened beings. According to Chapter 43, birth is simply the "union of body and senses," while death is their "separation." For most, death is an inseparable consequence of birth. However, for great souls like Sai Baba who "place their feet on the head of Time," these concepts are considered "false imaginations." The text clarifies that they incarnate by their own will, driven by a desire for the welfare of devotees, and are therefore not touched by the cycle of birth and death. For such a being, who has turned the body to ashes in the fire of Yoga even while living, "death is like dust before him."