That's something that only the mind can think about, that we don't actually have in the world, the empirical world itself.

那仅仅是心灵可以设想的东西,而在现实的经验世界中,却是不可能存在的

耶鲁公开课 - 死亡课程节选

Keep Him in mind if you say it, and Him only, and Him as He was and not as you'd like Him to have been.

把他放在心中如果你说的话，而且只有他，他应该是本来的样子，而不是你设想的他的样子。

耶鲁公开课 - 1945年后的美国小说课程节选

Look. Suppose we try to imagine a world in which Shelly exists but Kagan doesn't.

设想在某个世界里面,薛立存在而卡根不存在

耶鲁公开课 - 死亡课程节选