Selection

In addition to handwriting, the other important characteristic with which officials of the Tang dynasty were favorably promoted was having an excellent book knowledge.

In that era of China, it meant knowledge in history, literature, and philosophy (of Confucius, and possibly Zhuangzi [莊子]).

This was, again, a tradition set up by Li Shimin (李世民).

Yes, you are entirely right. The system was not perfect. How could one ascertain translation of book knowledge to practical administration ? Nonetheless, isn't this system somewhat similar to the philosopher king proposed by Plato ? Similarly, most of the senior officials and political leaders of the British empire study history or philosophy in Oxford or similar places.

You may argue many of our senior officials do have a university degree. Well, yes, degree, but how many of our degree holders do have the corresponding education ? They are the same on a superficial look, but, as Liji (禮記) said: 鸚鵡能言，不離飛鳥.

PS. In the original Tang system, students who did well in the Imperial Examination (科舉) had to stay in Chang'an (長安) for a year or two to learn the political system of the empire and receive training on administrative skill before they could be sent to take up some junior posts of the government.