 Non-realism can take many forms, depending on whether or not it is the existence or independence dimension of realism that is questioned or rejected. The forms of non-realism can vary dramatically from subject-matter to subject-matter, but error-theories, non-cognitivism, instrumentalism, nominalism,relativism, certain styles of reductionism, and eliminativism typically reject realism by rejecting the existence dimension, while idealism, subjectivism, and anti-realism typically concede the existence dimension but reject the independence dimension. Philosophers who subscribe to quietism deny that there can be such a thing as substantial metaphysical debate between realists and their non-realist opponents (because they either deny that there are substantial questions about existence or deny that there are substantial questions about independence).