Scientists, historians, economists, novelists and poets describe what they discover, experience and imagine. Specialists in each field disagree about the content of their description; or where there is agreement, alternative accounts remain at least a possibility. Also, it is clear that the scientist, the historian and the poet would present the 'same scene" in quite different ways, even if we should be reluctant to speak here of disagreement. There might seem to be no limit to the possible variety of accounts, within any field or among different fields. Yet it is no mere sophistry to say that we must be alike in general before we can be unlike in particulars. We must have the same language (however vaguely) for me to say "yes' where you say "no". We must both submit to space for one of us to be taller. We must both inhabit history for one to be more old-fashioned.