First, the teaching of rebirth makes sense in relation to ethics.
For early Buddhism, the conception of rebirth is an essential plank of its ethical theory,
providing an incentive for avoiding evil and doing good.
In this context, the doctrine of rebirth is correlated with the principle of kamma,
which asserts that all our morally determinate actions, our wholesome and unwholesome deeds,
have an inherent power to bring forth fruits that correspond to the moral quality of those deeds.
Read together, the twin teachings of rebirth and kamma show that a principle of moral equilibrium obtains between our actions and
the felt quality of our lives, such that morally good deeds bring agreeable results, bad deeds disagreeable results.
It is only too obvious that such moral equilibrium cannot be found within the limits of a single life.
We can observe, often poignantly, that morally unscrupulous people might enjoy happiness, esteem, and success,
while people who lead lives of the highest integrity are bowed down beneath pain and misery.
For the principle of moral equilibrium to work, some type of survival beyond the present life is required,
for kamma can bring its due retribution only if our individual stream of consciousness does not terminate with death.
Two different forms of survival are possible: on the one hand, an eternal afterlife in heaven or hell, on the other a sequence of rebirths.
Of these alternatives, the hypothesis of rebirth seems far more compatible with moral justice than an eternal afterlife;
for any finite good action, it seems, must eventually exhaust its potency, and no finite bad action,
no matter how bad, should warrant eternal damnation.
It may be the case that this insistence on some kind of moral equity is an illusion, an unrealistic demand
we superimpose on a universe cold and indifferent to our hopes.
There is no logical way to prove the validity of rebirth and kamma.
The naturalist might just be right in holding that personal existence comes to an end at death, and with it all prospects for moral justice.
Nevertheless, I believe such a thesis flies in the face of one of our deepest moral intuitions,
a sense that some kind of moral justice must ultimately prevail.
To show that this is so, let us consider two limiting cases of ethically decisive action.
As the limiting case of immoral action, let us take Hitler, who was directly responsible for the dehumanizing deaths of perhaps ten million people.
As the limiting case of moral action, let us consider a man who sacrifices his own life to save the lives of total strangers.
Now if there is not survival beyond death, both men reap the same ultimate destiny.
Before dying, perhaps, Hitler experiences some pangs of despair; the self-sacrificing hero enjoys a few seconds knowing he's performing a noble deed.
Then beyond that — nothing, except in others' memories. Both are obliterated, reduced to lifeless flesh and bones.
Now the naturalist might be correct in drawing this conclusion, and in holding that those who believe in survival and retribution are
just projecting their own wishes out upon the world.
But I think something within us resists consigning both Hitler and our compassionate hero to the same fate.
The reason we resist is because we have a deep intuitive sense that a principle of moral justice is at work in the world,
regulating the course of events in such a way that our good and bad actions rebound upon ourselves to bring the appropriate fruit.
Where the naturalist holds that this intuition amounts to nothing more than a projection of our own ideals out upon the world,
I would contend that the very fact that we can conceive a demand for moral justice has a significance that is more than merely psychological.
However vaguely, our subjective sense of moral justice reflects an objective reality, a principle of moral equilibrium that is not mere projection but is built into the very bedrock of actuality.