Political scientists have a tough time coming up with a definition of "politics". So, why not write another book?
Idealism often clashes with nature. Early societies were centered around close kinship and tribalism. All animals typically have an aversion to incest; therefore, in humans, the men who protected the tribe would trade women with neighboring tribes. Natural behavior, such as paternity fraud, can be deeply problematic. The desire for status is an evolutionary force. A side effect of that is rampant envy. Laws are adopted to avoid chaotic anarchy. As societies grow, hierarchies are established. Nepotism remains a natural process. Soldiers and slaves are forced to serve. Nations fiercely defend their borders. The best nations have institutions that promote economic prosperity and have laws that apply to everyone (even the lawmakers). Would global governance lead to more cohesiveness? Or would it degrade the local social fabric?
Political thinkers do not like to talk about biology or genetics. They tend to prefer blank slates in which to perform social engineering. The truth is that a policy will go extinct if it does not improve the widespread survival and reproduction of the people.