The analogy in this excerpt suggests that life is an illusion. Macbeth compares life to a "walking shadow" and a "poor player" who only performs for a short time before being forgotten, emphasizing a sense of emptiness and futility. The mention of "a tale told by an idiot, full of sound and fury, signifying nothing" reinforces the idea that life lacks true meaning or substance. Therefore, the most appropriate response based on the excerpt is:
That it is an illusion.