Final answer:
The use of allusion in the passages is significant as it creates deeper meaning by indirectly referencing religious symbols or Greek epics to add layers of significance and character depth.
Step-by-step explanation:
The use of allusion in the passages provided is key to understanding the effect and meaning the authors intended. An allusion is an indirect or implied reference to another work or idea, outside of the text, that isn't explicitly named. For example, Abraham Lincoln's phrase "sacrifice upon the altar of freedom" is an allusion to religious symbols, which adds a layer of significance by linking Mrs. Bixby's losses to a higher purpose or cause. Similarly, when an author such as Stephen Crane uses allusions to Greek epics, it is meant to convey certain attributes or thematic elements, such as the qualities of soldiers or the idealistic hopes of a character like Henry. This technique enriches the text by weaving in cultural or historical references that can provide depth to characters and their experiences.