How we cite our quotes: (Page.Paragraph)
Quote #1
This first stage of the mythological journey—which we have designated the "call to adventure" —signifies that destiny has summoned the hero and transferred his spiritual center of gravity from within the pale of his society to a zone unknown. (47.4)
This is definitely the sign that destiny is calling the shots, at least early on. Fate selects the hero, and the hero can only react to the summons. Free will only enters the picture if the hero refuses the call…and even then, fate has some nasty ways to get the hero back in line.
Quote #2
The hero can go forth of his own volition to accomplish the adventure, as did Theseus when he arrived in his father's city, Athens, and heard the horrible history of the Minotaur; or he may be carried or sent abroad by some benign or malignant agent, as was Odysseus, driven about the Mediterranean by the winds of the angered god, Poseidon. (47.4)
Once the call goes up, the hero can sometimes accept it of his own free will, in which case he or she's acting in concert with fate. Other times, fate just grabs the hero and carries him or her off, which puts the hero in a more adversarial position with fate.
Quote #3
Often in actual life, and not infrequently in the myths and popular tales, we encounter the dull case of the call unanswered; for it is always possible to turn the ear to other interests. (48.3)
There's always free will involved, especially here, when the adventure is just starting. The irony is that exercising free will by refusing the call only hurts the hero, not the rest of the universe.