Say you have an ancestor called John Smith, who lived in a small parish in the West of England. You know the year of his baptism, you know the place, you even know his parents' names, so you merrily head off to the internet/county record office to search for him. You find him, and are about to input his name into <insert name of genealogical software here>.
John, son of Thomas and Mary Smith. And, right underneath his baptismal entry, is another John, son of Thomas and Mary Smith. Is it the same one? Was the parish clerk forgetful, and/or seeing double? You turn the page. There's another John, son of Thomas and Mary Smith. This is where negative proof comes in. In order to make sure that you have the right John, you have to prove that all the other Johns were not 'yours' - within a radius of about 15 miles is about right. Or, if you are doing a Surname Study, you have to prove that all these Johns were indeed separate individuals and not the result of the clerk having the flu and not seeing straight.
Or maybe you have found what looks like John, son of Thomas and Mary Smith. But those names are not exactly unusual, so the logic of negative proof is to search all the registers around, to make sure there are no other John-son-of-Thomas-and-Mary-Smiths.
Of course, if your ancestor is called Severus Adolphus Ambrose Smith, you are unlikely to come up against too many duplicates.
© 2016 Ros Haywood. All Rights Reserved