The virtues we acquire, which develop slowly within us, are the invisible links that bind each one of our existences to the others - existences which the spirit alone remembers, for Matter has no memory for spiritual things.
We are the makers of our own lives. There is no such thing as fate. Our lives are the result of our previous actions, our karma, and it naturally flows that, having been ourselves the makers of our karma, we must also be able to unmake it.
Still others commit all sorts of evil deeds, claiming karma doesn't exist. They erroneously maintain that since everything is empty, committing evil isn't wrong. Such persons fall into a hell of endless darkness with no hope of release. Those who are wise hold no such conception.
Unless you see your nature, you shouldn't go around criticizing the goodness of others. There's no advantage in deceiving yourself. Good and bad are distinct. Cause and effect are clear. But fools don't believe and fall straight into a hell of endless darkness without even knowing it. What keeps them from believing is the heaviness of their karma. They're like blind people who don't believe there's such a thing as light. Even if you explain it to them, they still don't believe, because they're blind. How can they possibly distinguish light?
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
From a Buddhist point of view, the actual experience of death is very important. Although how or where we will be reborn is generally dependent on karmic forces, our state of mind at the time of death can influence the quality of our next rebirth. So at the moment of death, in spite of the great variety of karmas we have accumulated, if we make a special effort to generate a virtuous state of mind, we may strengthen and activate a virtuous karma, and so bring about a happy rebirth.
Jnana, bhakti, yoga and karma - these are the four paths which lead to spiritual freedom. One must follow the path for which one is best suited. But in this age, special stress should be laid on karma yoga.