Unproven vs. Unsubstantiated [closed]

Watching Meet the Press today I watched Chuck Todd insist that an accusation was unproven, but not unsubstantiated. What is the difference between these terms?

"You have firsthand accounts. They're unproven but they are not unsubstantiated. You have a, you have a first-hand account. We have somebody that disagrees with that first-hand account. But they are substantiated, no?" - Chuck Todd

http://www.nbcnews.com/meet-the-press/meet-press-october-16-2016-n667251

Solution 1:

In your quotation, the speaker is using 'prove' in the sense of 'definite conclusion from facts' and 'substantiate' in the sense of 'support with evidence', where evidence does not amount to a totally rigorous proof but only provides some degree of reason for us to believe something.

'Substantiated' can also be properly used to mean 'proven', which was likely the cause of confusion between Todd and Pence during the interview.

Solution 2:

Uncorroborated would likely be the best word with which both Todd and Pence could agree.

Todd was dancing on the head of a pin because the charges were detailed though uncorroborated, Pence feeling that the charges were lacking support, hence unsubstantiated (e.g., no witnesses, no smoking gun).