Realism remains one of the most important theories of international relations, despite others that aim at hacking away at its power hungry core with no real success.

Realism is the conservative theory of international relations that has maintained its place throughout the development of modern political science. Its premise is that all states are rational actors and their main goal is to attain power to survive.

There are five basic assumptions that explain the realist theory.

Anarchy

The world is anarchic, meaning that there is no global government. A government is a means of protection for citizens living within a community. Citizens within a nation depend on government for protection from outside threats from other nations or rogue actors, like terrorists. Because there is no global governance, it is important for a nation to have as much power as it can to ensure that its citizens are protected.

Maintaining Sovereignty

Nations want to rule themselves, or to remain sovereign, to pursue their own domestic destinies. If a nation is constantly battling the imposition of another, it can't focus on its own domestic affairs. If a person is constantly worrying about being fired (power struggle) then they act differently in regards to raising his or her children, perhaps by skimping, sending them to bad schools, or making them work to help out. However, if a person doesn't have to worry about money (security) then they can send their kids where they want, have money to buy them what they need, and make decisions for the household that they want to make.

Military

The most common way for a nation to achieve protection and domestic freedom is to have a strong military. Any type of military is essential for protection, whether it is strictly defensive, like that of Mexico, or both defensive and offensive like the United States' military. The stronger the military, the less chance there is that another nation will attack.

However, this leads to paranoia in the world. Many questions arise, such as why "Nation A" needs so many nuclear weapons if they are only trying to protect themselves. In theory a nation only needs as many weapons as its closest enemy. When it starts building more, questions arise about their true intentions and whether they are defensive or secretly offensive.

Transparency

A nation's intentions need to be disclosed so that other nations can act accordingly. If a state is transparent, or open about all of its actions such as arms building or joining an alliance, then its enemy will know what it is up to, and can act accordingly. However, even when a nation's leader gives an official statement about promoting a given policy, skepticism still ensues. For example, no too many people believed that the Iranian government was using nuclear technology for domestic energy even though this was the government’s official declaration. In a card game, if you tell everyone else what cards you have, then you lose leverage to win the game, or power to bluff your way through it. In addition, you could be lying about what cards you have, therefore accepting that your opponents could be lying about their cards too. Negative behavior is hard to control internationally because there is no way to punish it.

Survival

Therefore we circle back to the original idea of survival. Considering all of the above, a state’s goal is to survive and to figure out what it needs to do in order to stay one step ahead of everyone else. Realists believe that there is no room for ethics in the international arena, and that everything that can be done is done to gain power.