Final answer:
Hakuin Ekaku is credited with the Zen koan, "What is the sound of one hand clapping?" a riddle designed to transcend logical thought and aid in the realization of Zen enlightenment. Comprehension of this koan requires years of meditative practice.
Step-by-step explanation:
Hakuin Ekaku is renowned for formulating one of the most enigmatic Zen koans: "What is the sound of one hand clapping?" This koan proposes a riddle to meditators to challenge their attachment to logical thinking and aid their progress towards enlightenment. The concept of a koan compels a practitioner to transcend dualistic thought and embrace the non-conceptual wisdom of Zen. Understanding the koan involves a deep spiritual and intellectual commitment that is said to take years, often requiring extensive meditation and reflection.
Koans serve as a critical tool in Zen Buddhist practice and are integral to the introspective journey towards realizing the nature of the self and the universe. Hakuin's particular koan can take a student three years or more to comprehend, as it does not have a conventional answer. Rather, it is meant to aid in experiencing the essence of Zen, which is beyond words and rationalizations, through direct, non-intellectual understanding.