Most people who have been exposed to the social sciences have heard of a theory known as
social constructionism. It comes down to the thought that much of our social lives amount to social constructions: major parts of our behaviour, ideas and thoughts are defined by categories (nation, philosophy, politics) that have been constructed over time in different ways. This is often contrasted to
essentialism, which suggests that certain behaviours or patterns are innate or biologically determined.
In international relations (IR), there's a riff on social constructionism called
constructivism, which focuses on what political scientist
Benedict Anderson calls
imagined communities. These communities, or
imaginaries, are socially constructed ideas that give our lives shape. Think of the way our governments are formed, or the demands made of us by democracy, pluralism or multiculturalism (depending on our country). These aren't innate ideas – they are imaginaries. Not in the sense that they are not real, but in the sense that we developed them over time and they exist entirely in our heads. Borders don't show up in space – they exist in our minds and are made 'real' by being built into our institutions, architecture and documents.
But constructivism is also broader than this – it also refers to the strategies we have for life that we form through shared principles, norms, rules and conduct. These can be expressed through the law, which is one way of shaping our communities. We also have social values communicated through institutions like schools, religious centres and art spaces. Constructivists look at the ways these structures have been built, and the post-WWII era was a fertile period for all sorts of construction. With decolonization, many societies were regaining their freedom for the first time in decades (or even centuries) and the process of constructing a whole state was happening before our very eyes.
While we won't get into it too much right now,
deconstructionism took root a bit later. It started in linguistics and later spread to philosophy, critical theory, the arts and political science – in a nutshell it's about radically challenging the way certain things have been constructed. Many challenged status quo constructions because of perceived inequalities and power imbalances, and this led to Marxist (focused on class), feminist, racial and postcolonial theories emerging to challenge what they saw as various histories of oppression or exploitation built into the very construction of society.
Identity is key here, because many of these ways of challenging dominant constructions were tied to various groups a person belonged to: women, colonized peoples, the working class. And identity sometimes became a flag to rally behind in order to work towards a different type of system. This, for obvious reasons, has led to conflict.
For the first part of the 20th century one of the main paradigms in political theory was something called
realism, which focuses on how power works on the state level. Think ideological tussle-matches between the USA and USSR and their proxies, or different alliances and deterrents. This was a relevant framework for a long time, but the increasing amount of ethnic conflicts (often motivated by identity, among other factors) leading to civil and transnational wars has led to a need to look at other factors than states. After the horrors that took place in Rwanda and Bosnia in the early-to-mid 1990s, identity was one factor that started being investigated significantly more than before.