Book II marks the beginning of the Fellowship’s adventure. They are to proceed southeast to annihilate the Ring.
Their success relies on their hearts.
What is its function? The heart is the key to relationship building; the Ring is the key to relationship destroying. The heart is the source for blood, and the blood circulates the flesh. Therefore, it ordains every movement of every body part. Every movement shapes one’s identity: either as a warm-hearted or a cold-blooded being.
Such peregrination relies on the warm-hearted. It demands battling selfishness with selflessness—as the menacing road calls for great sacrifice—not by outer strength, but inner strength. The external factors are corporeal. But the internal factors lies in the heart, which steers the external.
Sauron recognized this: the supreme tack to demolish the forces of good is to strike the heart, which is the authentic part of sentient beings, the dominator of emotions, and the monarch of deeds. In the absence of a heart, there will be no authenticity and emotions, but a mere automaton. With an altered ticker, akin to the Ringwraiths, comes jeopardy.
Elrond healed Frodo from a calamitous venom that targeted his heart, which could prospectively renew him into a Ringwraith. If Frodo’s heart were metamorphosed, the entire stratagem for the Ring would collapse.
The core of the followers of Jesus, too, is in the heart. Tolkien understood that the dividing line between his theology and distinct creeds is the emphasis between the heart and the deeds. He believed that a heartless person with perfect acts will not be saved, but the one with a faithful heart with imperfect acts will be saved.
Character is a product of what one believes with all their heart, as revealed by the hearts of the dramatis personae of Middle-Earth.