...when it became necessary to do so
(...quando se tornou necesserário fazê-lo
.) [OU fazer isso.]It is our nature to do so.
But much of our thinking, left to itself, is biased, distorted, partial, uninformed, or downright prejudiced.
E (da) nossa natureza fazê-lo (ou -fazer isso.)...
... http://www.criticalthinking.org/pages/o ... inking/411do soto do what has just been mentioned
Synonyms or related words for this sense of so