Where does a cloud end and the sky start? How many hairs can a bald man have? The answers depend on the definition. You could say that a cloud ends when the percentage of water vapor is below a certain point. You could say that it ends when you can see through it. But opaqueness varies from different vantage points. Are men bald only when they have no hair at all? How much fringe do you need to not be bald? The more you think about these questions or try to define them, the less you understand. These are ambiguous, nebulous thoughts, the answer depends on the context.