Which of the following works of Plato has NOT been read so far?

The work that has not been read so far is "Critique of Pure Reason." This is because "Critique of Pure Reason" is a seminal text by the philosopher Immanuel Kant, not Plato. Kant's work fundamentally addresses issues in epistemology and metaphysics, focusing on the limits and scope of human understanding and reason.

In contrast, the other texts listed—"Euthyphro," "The Republic," and "Symposium"—are all written by Plato. "Euthyphro" explores piety and justice through Socratic dialogue, "The Republic" outlines Plato's vision of a just society and the philosopher-king, and "Symposium" discusses love and its nature through various speeches at a dinner party. Each of these works contributes significantly to ancient philosophy and Plato's ideas but does not relate to Kant's critical philosophy found in "Critique of Pure Reason."