There are the religious ones, the materialists, the dualists, the agnostics, the (insert any belief system here)... and I'm curious about what do YOU believe?
I'm highly skeptical, in the real sense, this is, I doubt we can have something called "knowledge" in the first place. That said, there are some labels I can live with (because, in the end, language is a boundaries game).
1) Instrumentalist; the belief about science is about successfully predicting facts, not about describing an objective reality.
2) Weak Social constructivist; scientific theories do not describe the nature of reality, they are just about the social construction of systems of propositions, methodologies and techniques to solve puzzles about the facts we encounter.
3) Model-Dependent Realist; it is meaningless to discuss about what reality "is", the only thing we can do is to contrast our models with facts, without imagining a concrete ontological status of anything behind them. Furthermore, every model can be from a different world view, incompatible with the others (eg, GR and QM), and this is ok simply because there is no a "final model" to achieve.
4) Advaitin; this is someone who believes there is no duality (subjectivity-objectivity) and that the individual experience is basically a "private virtual reality" or delusion. Everything is one and the same, and it is possible to experience it.
If I want to simplify my view to the max, it can be resumed like this:
Things are not. Things are seen.
Now, to understand why something can bee seen without the need for it "to be something in itself", its the key issue behind this ideas. Notice I don't say that their "being" consists in being perceived, a la Berkeley, who used this logic to say that everything was real but in the mind of god, opposing his idealism to materialism.
I'm saying something very different, things are seen, and this action is all that it is, or to put it in another way, contrary to the everyday common sense, things are the action between what we call the perceiver and what we call the perceived. Things are constructions based on observed facts, and facts are reality.