I wouldn’t call it a subjectivist framework. Members of Vienna Circle weren’t subjectivists. Ernst Mach and Bertrand Russell weren’t subjectivists. Heisenberg wasn’t a subjectivist. Yet, they all declared that there is nothing beyond experience, that metaphysics and ontology are nonsense, that physical objects do not exist as things-in-themselves but merely as groups of sensations, that theories are merely “economic summaries of facts”, that there is no a priori knowledge that wasn’t first discovered a posteriori, that we should stick to the facts instead of going beyond them (Occam’s razor) and so on and so forth. The correct name would be a phenomenalist framework (specifically that of Ernst Mach.) Ernst Mach wasn’t an idealist. He explicitly stated that those who think he’s an idealist are very far from understanding his position.
Realists, who are under attack in this thread, can only make sense if you understand that they do not understand the origin of their a priori knowledge. They don’t see how it’s derived from experience. Why? Because it is not them but their ancestors who derived it. That’s why they think that a priori knowledge has nothing to do with experience. Since they don’t understand how concepts of space, time and cause are derived from experience, they have no choice but to conclude that these concepts are not derived from experience.
They deny what is evident. That’s how you can identify them. They deny instrumentalism i.e. that theories are merely devices that generate predictions. Instead, they claim that theories are attempts to explain the universe (i.e. to find the underlying truth about the world.) They deny empiricism i.e. that theories are derived from experience. Instead, they claim that theories are conjectures formed independently from experience.
Truth depends on human judgment which may or may not depend on evidence. Subjectivists are people whose judgment about what’s going to happen does not depend on evidence but on what they want to happen e.g. I don’t want to die within next 500 years so I predict that I won’t die within next 500 years. Objectivists, on the other hand, are people whose judgment about what’s going to happen depends on evidence. So even if evidence suggests something unpleasant they accept it. That’s the real difference. As you can see, they both use human judgment albeit in a different way. You can say they use different methods of judgment. One is using preference-based judgment and the other evidence-based judgment.
I am not a subjectivist. I am an objectivist. But that does not mean I am a realist. I am an instrumentalist and a phenomenalist.
No, they are not floating around and they have nothing to do with Plato’s forms. One’s assumptions manifest through one’s behavior. By looking at how someone behaves you can tell what he’s assuming. Though you need a bigger picture than that, at the bottom, that’s how it works.