Final answer:
Gandhi's philosophy on non-violence is the central idea developed in Chapter 3 of 'The Story of My Experiments with Truth'.
Step-by-step explanation:
The central idea developed in Chapter 3 of Gandhi's The Story of My Experiments with Truth is Gandhi's philosophy on non-violence. In this chapter, Gandhi explores the concept of ahimsa, which is the practice of non-harming in Indian philosophy and religion. He explains how ahimsa guided his approach to civil disobedience and nonviolent resistance against the British colonial rule in India. Through his experiments with non-violence, Gandhi believed that embracing the principles of ahimsa and satyagraha can bring about social change without resorting to violence.