Final answer:
Oates' inclusion of a stranger testing the materiality of objects twice can indicate themes of reality versus illusion, existential inquiry, and a psychological struggle with discerning the real from the unreal, adding depth to character development and engagement with the text.
Step-by-step explanation:
In the context of the passages provided, Oates' description of the stranger touching something 'as if testing materiality' can suggest a number of underlying themes and devices used in literature.
Primarily, this act could be interpreted as an exploration of reality versus illusion, where the character seeks to confirm the existence or substance of things, questioning the nature of reality.
The stranger's action may symbolize a deeper existential inquiry, or it could highlight the character's detachment from the world or a sense of disbelief in what he perceives around him.
Moreover, this repeated motion of testing materiality might point towards the theme of uncertainty or a quest for truth within the narrative.
In a broader literary context, such actions can also reflect a character's psychological state, suggesting a feeling of alienation or estrangement from one's environment, which is often used to amplify psychological tension in a story.
Lastly, the act of touching objects to confirm their reality could also serve as a motif that echoes throughout the work, representing the character's ongoing struggle with discerning what is real from what is not, thus engaging readers in a more profound contemplation of the text.