请问presuppose在这句话中的意思？

leisure: 而不是 lesure

Tourism is a leisure activity which presupposes its opposite, namely regulated and organised work.

观光游览是可以预先假定是消遣的活动，也就是有系统的组织化活动。

例句与用法:
1. Only one person can do the job, namely you.
只有一个人能做这项工作，那就是你。

2. Only one boy was absent, namely Harry.
只有一个男孩儿缺席, 就是哈里.

3. Lydia briefly stated the business in hand, namely to choose a secretary and treasurer for the committee.
莉迪亚简单地陈述了马上要做的事，即为委员会选出一个秘书和财务管理人。

4. That is to say; namely.
也就是说；就是