  This entry treats experimental and theoretical work simultaneously with a bias in favor of those theoretical results that are unambiguously testable. It was once commonplace for even ecologists to accuse ecological theory of  untestability.[6]  This criticism was not completely fair even in the past; moreover, both experimental and theoretical developments during the last few decades have removed much of its force. Instead, what ecology poses is a much more philosophically intriguing set of seven problems: