Explanation:

- The passage discusses the nature of storytelling and its role in individual expression, likening it to a game between the author and the reader.

- The contract is described as an invention of Western civilization, focusing on creativity and individuality.

- The options provided for blank number 3 each suggest different characteristics that could relate to storytelling:

- Option 1, "plausible," implies realism or believability, which doesn't fit the theme of creating a personal paradise.

- Option 2, "imaginary," is about creativity and constructing worlds or ideas that may not exist in reality, which aligns with storytelling.

- Option 3, "drastic," suggests extreme measures or changes, which doesn’t pertain to invention or storytelling.

- Option 4, "transparent," refers to clarity and openness, which does not match the context of imaginative creation.

Thus, the word "imaginary" is most fitting for the context of creating a personal paradise within stories.