Beware duplicate sources—endeavor to uncover your source’s sources
You hear something. It’s fascinating. You yearn for it to be true, perhaps because it fits your hypothesis.
And then, from another second source, a source that doesn’t know your first source, you hear the same thing.
So you think it must be true.
Then it arrives from a third source, making it even truer?
From where are your sources getting their information?
Is it possible, though your sources do not know one another, they are getting their information from the same source?
Example: a liaison officer from CIA shares something of importance. As spymaster, you then learn the Italians believe the same.
Question: Are the Americans and the Italians receiving information from the same source?
Before you believe anything, you must identify your source’s sources and endeavor to discover if they are one in the same.
If you determine this to be so, it is called duplicate sourcing, which hampers the validation process.