That will,by necessity, need more troops, not only for the training, but for the mentoring in the field.

VOA: standard.2009.09.29

If they acted with a kind of mechanical necessity or even geometric necessity, they could not possibly be moral laws in that way.

如果这些法则有机械上,或者几何上的必须性的话，它们就不能被称作道德法则。

耶鲁公开课 - 政治哲学导论课程节选

It's definitely a necessity since there is not someone else there to help you with your kids.

VOA: standard.2009.12.04

Remember, everything we did was a first, not because we were pioneers or inventors, but it is literally, necessity is the mother of invention.

VOA: standard.2010.06.21