'Whether we deal with historical or natural phenomena, the individual observation of phenomena assumes the character of a 'fact' only when it can be related to other, analogous observations in such a way that the whole series 'makes sense.' This 'sense' is, therefore, fully capable of being applied, as a control, to the interpretation of a new individual observation within the same range of phenomena.
The passage argues that the interpretation of an individual observation relies on its connection to other similar observations within a larger context. This "sense" or pattern allows for consistent and meaningful understanding across different instances.