Inner disarmament, external disarmament; these must go together, you see. Peace is not just mere absence of violence - genuine peace must start in each individual heart.
If you develop a pure and sincere motivation, if you are motivated by a wish to help on the basis of kindness, compassion, and respect, then you can carry on any kind of work, in any field, and function more effectively.
From the scientific view, the theory of karma may be a metaphysical assumption -- but it is no more so than the assumption that all of life is material and originated out of pure chance