We all know that it’s important to avoid major grammar errors if we want to present ourselves in the best possible light, but it’s often subtle grammar errors that ultimately make the difference. Even when those subtle errors go unnoticed, they make the same difference that one off-key violin note might make to an orchestra. The average listener can’t pinpoint what’s wrong, but he knows that the performance wasn’t quite at its optimal level.
The incorrect usage of that instead of who when referring to a person is one of those subtle mistakes. John is the person that went to the store is incorrect, while John is the person who went to the store is correct. It makes complete sense to use who with a person and that with an obviously inanimate object, but sometimes, there are legitimate reasons for the confusion.
The media often uses that with a person, such as The person that robbed the bank also robbed the store because the media wants to dehumanize the report–they want it to be dry and factual, not human. While commonly used in that way, it’s wrong. A person, even a criminal, is animate.
There is also confusion about which to use when referring to animals–do they warrant a who or a that? That’s often a matter of personal opinion and usage. It’s hard to imagine that many of us would consider an ant to be a who; however, most of us probably consider good ol’ Rover to be a who. I’ve heard it recommended that named animals should be paired with who, and unnamed animals should be paired with that. In other words, both Whiskers is the cat who we all love and This is the cat that we all love would be correct.
Regardless of the instances of understandable confusion, there should be no confusion when dealing with people–while the point may seem debatable at times, we’re all worthy of being referred to as who rather than that.
–Paul
Paul’s book–Literally, the Best Language Book Ever


