The short answer is "very". The longer answer is that Vasudeva serves as Siddhartha's mentor and teacher. His name is another name for Krishna, a human incarnation of Vishnu, a Hindu deity. Vasudeva's name means "he in who all things abide and who abides in all." Thus he becomes Siddhartha's key to finding enlightenment. When Siddhartha remarks on the river's beauty, Vasudeva the ferryman responds, "I love it above everything. I have often listened to it, gazed at it, and I have always learned something from it. One can learn much from a river." He predicts Siddhartha's return.

More than twenty years pass before Siddhartha does return to the river and contemplates suicide. When the river revives his spirit, Siddhartha determines to remain near it. Remembering the ferryman who so loved the river, he asks to become Vasudeva's apprentice. As time goes on, Siddhartha's smile begins to resemble Vasudeva's—radiant, childlike, filled with happiness. Travellers mistake them for brothers; sometimes, when they sit listening together to the river, they have the same thought.