Intersubjective Realities
Across a range of fields, but especially (and most fundamentally) epistemology, “subjective” refers to things that are centered on an individual—including their personal opinions, biases, and emotions—while “objective” refers to the opposite: something that is demonstrably true and not filtered through an individual’s experience of reality.
So it’s an objective fact that Mount Everest is (approximately) 29,032 feet (8.849 meters) tall, but it’s a subjective claim if you say that Mount Everest is really, really huge and cold, and that climbing it was a difficult but life-changing experience.
Subjective claims are made from within the context of an individual, in other words, while objective claims are things we can confirm independently and which anyone can show to be true, if they have access to the right knowledge and/or tools.
“Intersubjectivity” refers to a type of subjective truth that emerges from groups of people, rather than individuals.
If several people climb Mount Everest together, they might all agree that the climb was brutal and cold and life-changing, and that might then form the basis of their collective sense of their shared experience; everything else is predicated on that agreed-upon conception of reality.
This term is often used to refer to larger shared understandings, though, like the sense of the world people within the same political party might subconsciously agree upon, acting as if their intersubjective reality is true even if it’s objectively not (by voting, for instance, or treating people from other parties as if they are monsters).
Subjectivity can cause us to behave strangely (through the lens of objective fact, at least) if we interpret a conversation with a neighbor to be antagonistic rather than just awkward: we might treat that neighbor as an enemy from that point forward, despite a lack of actual antagonism (though this misinterpretation could lead to antagonism on the part of the person who did the misinterpreting).
Intersubjectivity can cause the same, but on a far larger scale.
If a group of people all believe something that’s untrue, they might vote accordingly, and that false, shared belief could also change the nature of their other relationships, how they eat or worship or the work they do, and it might even lead them to commit acts of violence (in support of some perceived, intersubjective truth).
It could be argued that most religions (and other faith-based groupings) rely upon intersubjective realities for their persistence and expansion, and many relationships (friendships, romantic couplings, and even business relationships) may be predicated on intersubjective beliefs, as well, even if those beliefs are limited to things like “we can build a wonderful life together” and “we can be the dominant players in this industry” (despite there being no objective evidence for either claim).
Intersubjectivity may even form the basis of modern civilization, as we’ve all agreed to pretend that pieces of paper are valuable, groups of humans called governments are in charge, and invisible lines divide the planet up into (not real) things we call countries.
All of which are concepts that help us organize ourselves, manage scarce resources, and fight each other less than we might otherwise (though that point is debatable), but all of which also only persist and function because we collectively believe (or agree to pretend we believe) they’re real, which suggests our tendency toward biased thinking may be fundamental to our capacity to work together with other human beings.