Thomas Aquinas" writings of politics or philosophy, the importance of state or government is all mentioned in detail. All three great philosophers have different angles about what is the purpose of a state and why it exists. When all three of these great figures all agree state exist for people's common good, they have different angle of the nature and purpose of the state. Plato believes in a perfect government type for state and stresses the importance of state unity. Different from Plato, Aristotle thinks state is the highest stage of human community and doesn't think unity is that important as Plato says. Aquinas in some way remain and add Aristotle's thoughts into Christianity. Besides, he extend people's right in the state and introduce the concept state is subject to the church.
Plato and Aristotle have different understanding of why the state exists, so they interpret what is the purpose of the state too. In order to understand their different conclusions of political state, we need to be aware of their difference in world's view and philosophy. Plato believes in absolute truth in terms of morality and politics. Besides, Plato is only able to identify the difference between individuals in terms of three classes, which are producers, civilians and guardians. Plato favors the ideal of the absolute truth with very little concern whether such truth is practical or not. More than that, the truth to Plato seems to be unchangeable whether in ideas or philosophy. Plato believes the absolute truth can be applied to every aspect in the society including political organization.
Plato, whose political view can be found in his writing, Republic, focus on searching a perfect society. Plato thinks the state is a piece of self-regulating piece of machinery. Although Plato does believe a state should bring happiness to majority, he does not recognize that happiness means different to every people in the state.