Why is Jessica's 'Last Thursday' Theory Unscientific?

The correct answer is: Since there is no conceivable evidence that could ever prove her theory wrong, it is not falsifiable.

Jessica's theory is unscientific because it is not falsifiable. Falsifiability is an essential criterion in science, which means that a scientific theory must be able to be disproven or proven wrong through empirical evidence. In Jessica's theory, she claims that all evidence of events before last Thursday was created at that time, making it impossible to provide any evidence that could potentially disprove her theory. This lack of falsifiability makes her theory unscientific.