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
To find Buddha, you have to see your nature. Whoever sees his nature is a Buddha. If you don't see your nature, invoking buddhas, reciting sutras, making offerings, and keeping precepts are all useless. Invoking buddhas results in good karma, reciting sutras results in a good memory, keeping precepts results in good rebirth, and making offerings results in future blessings-but no Buddha.
I am the owner of my actions, heir to my actions, born of my actions, related through my actions, and have my actions as my arbitrator. Whatever I do, for good or for evil, to that I will fall heir.
Surely if living creatures saw the results of all their evil deeds, they would turn away from them in disgust. But selfhood blinds them, and they cling to their obnoxious desires. They crave pleasure for themselves and they cause pain to others; when death destroys their individuality, they find no peace; their thirst for existence abides and their selfhood reappears in new births. Thus they continue to move in the coil and can find no escape from the hell of their own making.
Who cares for your bhakti and mukti? Who cares what your scriptures say? I will go into a thousand hells cheerfully if I can rouse my countrymen, immersed in tamas, to stand on their own feet and be men inspired with the spirit of karma-yoga. I am a follower only of he or she who serves and helps others without caring for his own bhakti and mukti!
The natural laws of the universe are inviolable... what you say and do determines what happens in your life... You are the master of your life and death. What you do is what you are.
The way of presentation is different according to each religion. In theistic religions like Buddhism, Buddhist values are incorporated. In nontheistic religions, like some types of ancient Indian thought, the law of karma applies. If you do something good, you get a good result. Now, what we need is a way to educate nonbelievers. These nonbelievers may be critical of all religions, but they should be decent at heart.