For the most part, my dad was very , rarely showing his emotions; but once in a while he would grow and sentimental about the past.

Stoic ; wistful

Explanation:

Being stoic is being calm and almost without any emotion. When you're stoic, you don't show what you're feeling and you also accept whatever is happening.

wistful is having sadness or melancholy about something. it is having a mournful or regretful longing.

answer; /// i believe that the correct answer is(cognitive revolution);

classical republicanism, also known as civic humanism, is a form of republicanism  developed in the renaissance inspired by the governmental forms and writings of  classical  antiquity, especially such  classical  writers as aristotle, polybius, and cicero.