It has to be part of a theory, and then trying to adjust it so it can be incorporated, you discover anti-particles.

要想使理论合理,然后试着去调整,使之和实际相符,结果就找到了反粒子

耶鲁公开课 - 基础物理课程节选

You've got to think about what they mean, and that's one of the best things about physics because here's a person who is not looking for anti-particles.

你得去思考它们的意义,这是物理学最美妙的地方,因为有位仁兄本不是去找反粒子的

耶鲁公开课 - 基础物理课程节选

There it meant something much more interesting, mainly anti-particles accompanying particles.

而那里说的是一些更有趣的东西,大多数反粒子与粒子成对出现

耶鲁公开课 - 基础物理课程节选

And it turns out the second solution, with negative energy, was when the theory is telling you, hey, there are particles and there are anti-particles, and the negative energy when properly interpreted will describe anti-particles.

结果,后来证明,第二个根,也就是能量为负的那个根,正是理论的关键,世界上既有粒子,也有反粒子,负能量就是用来解释反粒子的

耶鲁公开课 - 基础物理课程节选