What does the term "rational unitary actor" mean?
 

Respected members,I came across this term while reading "Approaches to explaining International relations"(realism,liberalism etc)
According to Realist of though,a state is a rational unitary actor, while liberalism states,"a state needs not necessarily be a unitary and rational actor".But I don't understand the meaning of the term "rational unitary actor".If any one of you could kindly explain it's meanings?

regards

Realists thought advocates that a state should not be dependent on another state by any means, thus it becomes a Unitary rational unit, examples could be derived from the time of Industrial revolution i.e, Britain, France, Spain required raw material to run their industries effectively, however, since they did not want to depend on each other because they were bitter enemies and competitors in race to power, they headed in different directions to seek the raw material. Realism basically is a zero-sum game. If it is good for me it is bad for you.

Liberalism on the other hand promotes mutual cooperation in order to achieve goals, so inter-dependence does occur, and hence the nations cannot be considered as unitary.