Continuum fallacy is a logical fallacy where one improperly rejects a claim because it is not clearly distinguishable from another claim. This fallacy assumes that because there is no clear dividing line between two things, there is no real difference between them. It disregards the possibility of a gray area or a spectrum between distinct categories.
For example, someone might say, "There's no real difference between a 17-year-old and an 18-year-old. One day doesn't magically make someone an adult. So, the legal drinking age or voting age is arbitrary and meaningless." In this example, the speaker argues that because there's no dramatic change in a person's maturity between the day before and the day after their 18th birthday, the legal distinction between a minor and an adult is invalid. This ignores the social and legal conventions that establish a specific age for these rights and responsibilities. The fallacy lies in assuming that because the transition to adulthood is gradual, a defined legal threshold is inherently meaningless.