In all discussion of metaphor, writes H. W. Fowler in Modern English Usage , it must be borne in mind that some metaphors are living, i.e., are offered and accepted with a consciousness of their nature as substitutes for their literal equivalents, while others are dead, i.e., have been so often used that speaker and hearer have ceased to be aware that the words used are not literal.
The writer claims some metaphors are living.