"Master" means to them, as "_Mister_" Haggin meant to Jerry, a deal more, and a great deal more, than it means to humans.

The human considers himself as "master" to his dog, but the dog considers his master "God." Now "God" was no word in Jerry's vocabulary, despite the fact that he already possessed a definite and fairly large vocabulary.

"_Mister_ Haggin" was the sound that meant "God." In Jerry's heart and head, in the mysterious centre of all his activities that is called consciousness, the sound, "_Mister_ Haggin," occupied the same place that "God" occupies in human consciousness.

By word and sound, to Jerry, "_Mister_ Haggin" had the same connotation that "God" has to God-worshipping humans.

In short, _Mister_ Haggin was Jerry's God.
And so, when _Mister_ Haggin, or God, or call it what one will with the limitations of language, picked Jerry up with imperative abruptness, tucked him under his arm, and stepped into the whaleboat, whose black crew immediately bent to the oars, Jerry was instantly and nervously aware that the unusual had begun to happen.