There is an incident that really ought to be reported. It occurred today, at the second-closest grocery store to my home.

The man in front of me wanted to return some breast feeding product he had purchased for his girlfriend, no less than a week before. He was short a receipt, but, apparently, spoke with the manager of the store who said it would be OK for him to return the product. When this story was relayed to the cashier, she phoned her supervisor. He came over, listened to the story, and told him that he could not make the exchange.

'But it is $13. That is a lot of money.'
'I know it is a lot of money. That is exactly why I cannot make the return without the receipt.'

What irks me most about the exchange is that the predicate, 'is a lot of money', is vague. Which quantities satisfy it depend on context. The supervisor responded as if the predicate were context insensitive. His not allowing the return was voiced as a consequence of the fact that the predicate had those properties. But it does not. So the reason did not license the conclusion.