Synthesized answer
The provided passages do not explicitly state the central thesis of "Ficciones" by Jorge Luis Borges.
However, the description of the collection indicates that Borges "often uses the labyrinth as a literary device to expound his ideas on all aspects of human life and endeavor" [Passage 1]. This suggests that the exploration of human life and endeavor through the metaphor of a labyrinth is a significant theme within the work.
Synthesized from the book passages below. Chat with the book on Feynman for follow-up.
From the book
Title: Ficciones by Jorge Luis Borges Description: A collection of his short stories in which Borges often uses the labyrinth as a literary device to expound his ideas on all aspects of human life and endeavor. ---------- Contains: [Tlön, Uqbar, Orbis Tertius](https://openlibrary.org/works/OL444914W)