After the robbery of Silas Marner's gold the town of Raveloe was divided in their different opinions of who committed the robbery. One part of Raveloe insisted in that there was once a peddler who came through the village selling stuff to everyone. As the story snowballed from mouth to mouth, everyone who believed it already had a set notion that this peddler had to be the culprit, since he was likely a traveling gypsy whom they unanimously decided to describe as a man wearing earrings and with a weird look about him.
The other side of Raveloe was actually conjuring many impossible theories, such as providence or divine intervention, changelings, and many things that were highly impossible and improbable.
Hence, those who went with the peddler theory would call the ones with the improbable theory mush-brained, and those who believed in the impossible theories treated those who believed in the peddler theory like "animals that cow before finding corn".