Sometimes called the Quine–Duhem or Duhem-Quine thesis. The thesis that a single scientific hypothesis cannot be tested in isolation, since other, auxiliary hypotheses will always be needed to draw empirical consequences from it. The Duhem thesis implies that refutation is a more complex matter than might appear. It is sometimes framed as the view that a single hypothesis may be retained in the face of any adverse empirical evidence, if we are prepared to make modifications elsewhere in our system; although strictly speaking this is a stronger thesis, since it may be psychologically impossible to make consistent revisions in a belief system to accommodate, say, the hypothesis that there is a hippopotamus in the room when visibly there is none.