The premise of the law of karma is that the universe is not merely physical, but also moral. Cause and effect governs the physical aspects of our actions, there is natural law that governs the moral aspects of our actions. Tenzin Gyatso describes karma as “an instance of the general law of causality. What makes karma unique is that it involves intentional action, and therefore, an agent . . . In order for a causal process to be a karmic one, it must involve an individual whose intention would lead to a particular action.” Just as the law of gravity comes into play when two physical bodies come sufficiently close to one another, the law of karma comes into play when someone performs an intentional act that has the potential to harm or help a living being.
Norm Phelps
from The Great Compassion; Buddhism & Animal Rights