John Mearsheimer-Offensive Realism

John Mearsheimer is well-known international relations theorist and a professor of political science at the Univeristy of Chicago. The excerpted version of his prominent book, 'The Tragedy of Great Power Politics' is included in my textbook. Thus, I am writing down his introduction here.

By reading a part of his book, I knew his 'offensive realism.' It is the framework how countries act in the international politics.
He raises five assumptions on this.

The first assumption is that in the international politics there is no 'goverment over goverment.' He call the situation anarchic. Because there is no obligatioin to follow, and thus, there is no existance to trust in, states pursue power.
The second assumption is that states are potentially dangerous each other no matter they have much more weapons than others or not. The impressive and interesting sentence for me is 'After all, for every neck, there are two hands to choke it.' This really explains how much nations have to be careful and watch out what other nations are trying to do.
The thrid assumption is that states have no idea about other states' intentions. It is because intentions are impossible to divine with 100 percent certainty and can change quickly in his words.
The forth assumptioin is that the ultimate aim of states is to survive. Power comes along with seculity. Therefore, states pursue power to survive in the world.
The fifth assumption is that states are rational factors.

With such analysis, he proposes the reasons why states tend to pursue power.