复数： follies

So when depression economics prevails , prudence is folly .

所以当萧条经济蔓延的时候，精打细算的愚蠢的。

Is this just a moment of collective folly , a wilful blindness to the lessons of the past ?

这难道仅仅是一次集体愚行，仅仅是一时对过去经验教训的故意视而不见？

Would the american president still feel obliged to defend israel from the consequences of its own folly ?

美国总统还会认为他有义务保护以色列不为其所做的蠢事承担后果？

But that would be utter folly .

但是这是彻头彻尾的愚蠢想法。

Folly and ignorance play a part .

愚蠢和无知也起到了一定作用。