YOU SAID:

the stupidity of others is quite incredible

INTO JAPANESE

他人の愚かさはかなり信じられない

BACK INTO ENGLISH

I can not believe foolishness of others quite

INTO JAPANESE

私は他人の愚かさを全く信じることができません

BACK INTO ENGLISH

I can not believe the foolishness of others at all

INTO JAPANESE

私は他者の愚かさを全く信じることができない

BACK INTO ENGLISH

I can not believe the foolishness of others at all