Final answer:
Anarchy is the concept in international relations that there is no overarching global authority, leading to a system where states maintain their sovereignty and are ultimately self-reliant.
Step-by-step explanation:
The concept described in the question, where states are ultimately on their own in the world system with no global government or supranational organization more powerful than any state's military or economic power, is known as anarchy. This concept manifests in international relations where there is no overarching governing authority, making the international system anarchic. Within this system, states hold onto their sovereignty, the concept that allows states to chart their own path and embodies their status as independent and equal actors in the absence of a higher authority.