Thucydides (460BC or Earlier) is one of the earliest ancient Greek classical realist thinkers or scholars who contributed significantly to the field of International relations, state behaviour, and Relations between states.
Thucydides saw the inevitable competition and conflict between ancient Greek city-states (which composed the cultural-linguistic civilization known as Hellas) and between Hellas and neighbouring non-Greek empires, Such as Macedonia and Persia Neither the states of Hellas nor their non-Greek neighbours were in any sense equal.
On the contrary, they were substantially unequal; there were a few ‘great powers’ such as Athens, Sparta, and the Persian Empire, and much smaller and lesser powers, such as the tiny island statelets of the Aegean Sea. That inequality was considered to be inevitable and natural.
A distinctive feature of Thucydides’ brand of realism is thus its naturalist character.
Aristotle said that ‘man is a political animal’.
Thucydides said, in effect, that political animals are highly unequal in their powers and capabilities to dominate others and defend themselves.
All states, large and small, must adapt to that given reality of unequal power and conduct themselves accordingly. If conditions do that, they will survive and perhaps even prosper. If states fail to do that, they will place themselves in jeopardy and may even be destroyed. Ancient history contains many examples of small and large states and empires that were destroyed.
So, Thucydides emphasizes the limited choices and the restricted sphere of manoeuvre available to rulers in the conduct of foreign policy.
He also emphasizes that decisions have consequences before any final decision is made. A decision-maker should have carefully thought through the likely outcomes, bad and good.
In pointing that out, Thucydides is also emphasizing the ethics of caution and prudence in the conduct of foreign policy in an international world of great inequality of limited foreign-policy choices and ever-present danger and opportunity.
Foresight, prudence, caution, and judgment are the characteristic of the political ethics of classical realism that Thucydides and most other classical realists are at pains to distinguish from private morality and the principle of justice. If a country and its government wish to survive and prosper, they better pay attention to these fundamental political maxims of international relations.
In his famous study of the Peloponnesian War (431-404 BCE), Thucydides put his realist philosophy into the mouths of the leaders of Athens–a great power–in their dialogue with the leaders of Melos—a minor power–during a moment of conflict between the two city-states in 416 BCE. The Melians appealed to the principle of justice, which meant that the powerful Athenians should respect their honour and dignity as an independent state.
But, according to Thucydides, justice is of a particular kind in international relations. It is not about equal treatment for all because States are unequal. Instead, it is about recognizing your relative strength or weakness, knowing your proper place, and adapting to the natural reality of unequal power. Thucydides, therefore, let the Athenians reply to the
That is probably the most famous example of the classical realist understanding of international relations as basically anarchy of separate States that have no real choice except to operate according to the principles and practices of power politics in which security and survival are the primary values, and war is the final arbiter.