The Italian poet and scholar who invented the concept of historical distance — the idea that ancient Rome was a distinct civilization that had ended, not simply a continuous past — and whose recovery of classical texts and sense of historical belatedness made the Renaissance possible as an intellectual project.
Before Petrarch, medieval Europeans thought they were Romans — or at least the heirs of an unbroken tradition. After Petrarch, they understood they were not. He invented the idea that antiquity was over: that it had been a distinct civilization, different from his own, whose loss could be mourned and whose recovery could be attempted. That invention is the Renaissance.