Bankei Yotaku was a renowned Japanese Zen master who lived in the 17th century. He is known for his simple yet profound teachings, which emphasized the importance of direct experience and the innate Buddha nature within each individual. One of the key elements of Bankei's teachings was the use of koans.

Koans are paradoxical statements or questions that are used in Zen practice to help students break through their limited thinking and reach a state of enlightenment. In Bankei's teachings, koans played a crucial role in guiding his students towards a deeper understanding of their true nature.

Bankei believed that the mind is inherently pure and clear, but it becomes clouded by our attachments, desires, and delusions. Koans were used as a means to disrupt this clouded mind and bring about a state of clarity and awareness.

One of Bankei's most famous koans was "What is your original face before your parents were born?" This koan challenges the conventional concept of self and encourages students to look beyond their physical appearance and personal history to discover their true nature.

In his teachings, Bankei emphasized the importance of not getting caught up in intellectual understanding or trying to solve koans with the mind. Instead, he encouraged his students to let go of all thoughts and concepts and simply be present with the koan. This approach of non-thinking and non-dualistic awareness is at the core of Zen practice and is essential for understanding koans.

Bankei also used koans as a means of testing his students' understanding and progress on their spiritual journey. He would often give his students a koan and observe their reactions and responses, using it as a way to guide them towards a deeper understanding.

Furthermore, Bankei's use of koans was not limited to formal practice. He encouraged his students to apply the wisdom of koans in their daily lives, using them as a tool for self-reflection and mindfulness.

In conclusion, koans played a significant role in Bankei Yotaku's teachings. They were used as a means to disrupt the clouded mind, guide students towards a deeper understanding of their true nature, and test their progress on the spiritual path. Bankei's approach to koans was one of non-thinking and non-dualistic awareness, emphasizing the importance of direct experience and living in the present moment.