For will power directs energy, and energy in turn acts upon matter.
If we accept the principle of cause and effect in Nature, and of action and reaction in physics, how can we not believe that this natural law extends also to human beings? Once consciousness is understood as basic to everything the question begs to be asked: Do not humans, too, belong to the natural order?
Such is the law of karma: As you sow, so shall you reap. If you sow evil, you will reap evil in the form of suffering. And if you sow goodness, you will reap goodness in the form of inner joy.
To understand karma, you must realize that thoughts are things. The very universe, in the final analysis, is composed not of matter but of consciousness. Matter responds, far more than most people realize, to the power of thought. For will power directs energy, and energy in turn acts upon matter. Matter, indeed, is energy.
Every action, every thought, reaps its own corresponding rewards. Human suffering is not a sign of God's, or Nature's, anger with mankind. It is a sign, rather, of man's ignorance of divine law.
The law is forever infallible in its workings.