Thymos is a philosophical concept introduced by Plato as one of the three motivations of man, the first two being needs and desires. It is the emotional need for every human to be recognized by others as human, and deserving of respect. Megalothymia specifically is the need to be recognized as superior to others, while isothymia is the need to be recognized as merely equal to others.
These concepts are used by Francis Fukuyama in his book The End of History and the Last Man to justify his argument that liberal democracy is the ultimate political system. In order for people to exist in harmony, he argues, isothymia rather than megalothymia must be used to satisfy the human need for recognition. Any system that creates political inequality is necessarily feeding the megalothymia of some members while denying it to others. Liberal democracy, he suggests, can satisfy the isothymia of all people simultaneously, without creating conflict, leaving megalothymia only in the realm of economics.