A person wearing a sweater looks at a spill on some brick steps outside .
A person notices that he has left his keys at home .
A person wearing a sweater looks at a spill on some brick steps outside.
A person notices that he has left his keys at home.
A person looking a spill cannot at the same time realize he has left his keys at home.
A person looking a spill can not at the same time realize he has left his keys at home .