a8.1. Use who and whom in reference to people or animals with names (the man who set the fire; Waldo, who was adorable). (N.B.: Whom, though still grammatically correct, is evolving out of the language. Use only in an objective case: I know of whom you speak; Puckett spoke to whomever he saw on the way.)
a8.2. Use that and which to refer to inanimate objects
or animals without names (A poker chip, which was a major
clue; the mynah bird that bit her). (N.B. That is acceptable,
though not preferred, to refer to an unidentified person:
The doctor that operated on him. Never, however, use to refer to
an identified person.)