Not law. Not religion. Not custom. Dharma is the answer to a harder question: what does this situation, and my place in it, actually require of me?
The word is famously difficult to translate. Across the Indian traditions it carries senses of duty, right order, righteousness, the intrinsic nature of a thing, and the principle that holds a world together. The Mahabharata itself repeatedly stages the difficulty: its characters argue about dharma, and its most admired figures are the ones who find it hardest.
That difficulty is a feature. A rule can be obeyed without understanding. Dharma cannot, because it is situational: what is required of a judge, a parent, a soldier and a farmer differ, and what is required of each of them differs again by circumstance. It is closer to a form of judgement than to a code.
In this book I use it in a deliberately narrowed sense: dharma is responsibility correctly located. It asks what is mine to do — not everything, not nothing, but the specific part that falls to me because of where I stand, what I can see, and what power I hold.