the one I’ve heard is, a farmer can’t see his cow anywhere. his neighbor comes to visit, and on the way she walks past the farmer’s field and sees the cow behind (from the house’s perspective) a small patch of trees and brush. she doesn’t notice that on the other side of the trees (toward the house) there is a bedsheet caught in the low branches that was blown off of someone’s clothesline and fell in mud along the way. when she reaches the house the farmer asks if she’s seen the cow, she says yes, it’s over by the trees. the farmer looks out and sees the sheet in the distance, mistakes it for the cow, which he has not actually seen, and thus believes the neighbor. so the cow is by the trees, he believes the cow is by the trees, and he has good reason to believe, and yet based on the evidence actually available to him, he should not be certain