Epistemology is the branch of philosophy that deals with the nature, origin and scope of knowledge.
Futures studies came of age during the most recent attack on positivism (in 1970s) and futurists have been influenced by the postmodernists. However, postmodern theories of knowledge are flawed, breed nihilism and do not allow advancements in any scholarly field, including futures studies.
Wendell Bell suggests that critical realism is better suited for future studies, because it postulates that knowledge is conjectural without giving up the idea of "justified beliefs in the truth of propositions". Thus it is compatible with assertions about both present/past (where we have evidence) and the future (that doesn't even exist).
- Foundations of Futures Studies, Wendell Bell (available at Google Print)