This sentence means to evaluate historical figures from a historical perspective, not from the perspective of our time. For example, the evaluation of Wu Zetian. The evaluation of Wu Zetian in history is very poor, because China was a patriarchal society in ancient times, and women had no right to be emperors, so it must be a bad evaluation to evaluate Wu Zetian from a historical perspective. It is different to evaluate Wu Zetian from the perspective of today's society. Equality is advocated now, and women can be leaders. Therefore, we regard Wu Zetian as her contribution to history. From this perspective, Wu Zetian is a positive image, because she continued the rule of Zhenguan and laid the foundation for the prosperity of Kaiyuan, so Wu Zetian should be a positive historical figure.