What are the ethical principles of yoga, as outlined in the Yoga Sutras? How do they relate to modern yoga practice?

The Yoga Sutras of Patanjali is a foundational text of classical yoga that dates back to around 200 CE. Among its eight limbs or aspects of yoga, the first two limbs, called the yamas and niyamas, outline the ethical principles and values that are considered fundamental to a yoga practitioner's spiritual growth and development.

The yamas are the ethical guidelines or restraints that are meant to be observed in one's interactions with the external world. There are five yamas:

1. Ahimsa: Non-violence or non-harming. This principle includes refraining from causing harm to oneself, others, and all living beings.
2. Satya: Truthfulness. This principle entails being honest in one's thoughts, words, and actions.
3. Asteya: Non-stealing. This principle includes not taking anything that has not been given to us, whether material or non-material.
4. Brahmacharya: Self-control or celibacy. This principle refers to the appropriate use of one's energy, including sexual energy, and channeling it towards spiritual pursuits.
5. Aparigraha: Non-attachment or non-greediness. This principle involves letting go of the attachment to material possessions, people, and outcomes.

The niyamas are the ethical guidelines or observances that are meant to be observed in one's personal life. There are five niyamas:

1. Saucha: Cleanliness or purity. This principle includes maintaining cleanliness and purity in one's body, mind, and environment.
2. Santosha: Contentment or satisfaction. This principle involves finding contentment and gratitude in the present moment, rather than always seeking external sources of happiness.
3. Tapas: Self-discipline or austerity. This principle involves cultivating self-discipline and willpower to overcome obstacles and challenges in one's life.
4. Svadhyaya: Self-study or self-reflection. This principle involves reflecting on one's thoughts, emotions, and actions to gain self-awareness and understanding.
5. Ishvara pranidhana: Surrender to a higher power or divine consciousness. This principle involves letting go of the ego and cultivating devotion and surrender to a higher power.

In modern yoga practice, these ethical principles are often emphasized and incorporated into the practice through various means, such as discussion, reflection, and intention-setting. Practitioners may also seek to apply these principles in their daily lives and interactions with others. By doing so, they aim to cultivate a deeper understanding and connection to their true nature, as well as a greater sense of inner peace, compassion, and harmony with the world around them.