The character of being unthinking or thoughtless.(noun)
The Century Dictionary (Public Domain)
Use "unthinkingness" in a sentence
"'But as long as we have kept you alive, and saved you from being transported,' said his wife, 'for which all thanks be due to this good gentleman, we shall mind no hardships, and never go astray again, in wicked unthinkingness of this great mercy.'"
"And, truly, I was utter angered with myself; and somewise also with her, in that she did not waken mine unthinkingness to this thing."
"After the grim composure, and substantial, reflective methods of her New England life, the _abandon_ and unthinkingness of these French-Canadians were bewildering and delightful to her."