Next week, Paul has to go to Australia on business. He must visit the Opera House in Sydney before he comes back. While he is away, Cindy, his wife, must lose some weight. She has to stop eating chocolate.
What exactly is the difference between 'must' and 'have to'? Don't both express the idea of obligation when there is no choice about the action being done?
Paul does not have a choice about going to Australia. His boss has told him to go. The Sydney Opera House is a world-famous building and Paul would be a fool not to visit it. Cindy is getting fat and she has no choice but to lose weight if she wants to stay healthy. Eating chocolate is making her fat so she has no choice but to stop if she wants to get thin again.
Can we change 'must' and 'have to' around to mean the same thing in different sentences? Does it matter which one we use?
Tom has to get up early tomorrow morning.
Tom must get up early tomorrow morning.
Do these two sentences mean exactly the same thing? You have to look at them very carefully to see that they do not have the same meaning. 'Have to' expresses the idea of obligation coming from a third party, not from the person involved.