The reality is the same for all of us. Even those who are neither Buddhists, nor Hindus, are reborn, whether they believe it or not. At least they cannot deny that they have been born, can they? So the difference between Rebirth in Buddhism, and Re-incarnation in Hinduism is a matter of concepts. Hindus believe in an immortal soul that is transferred from one existence to the next. Buddhists do not believe in an eternal soul, but they do believe in rebirth. There is no eternal essence that remains unchanged throughout life, and even after death.
How Can Rebirth Take Place if there is no Soul?
A fair question, and an important concept to grasp correctly. It may be easiest to understand with the help of a simile. Take a match and a candle. Light the match. Now hold the candle wick directly over the flame, but not actually touching it. Watch closely what happens. After a few seconds the wick will begin to smoulder, and a flame will ignite. A child might say that the flame jumped from the matchstick to the candle, because that is what seems to happen.
A scientist would describe the process differently. He would perhaps say that due to the heat in the match flame, the paraffin wax in the wick vaporised, reached its ignition temperature, and begin to react with the oxygen in the air. This rapid process of oxidation produced the flame in the candle. Nothing jumped from the matchstick to the candle, but the heat was the cause produced by the oxidation of the wood, that led to the result, which was the oxidation of the paraffin wax and the second flame.
Rebirth is similar to this process. A living being does many volitional activities, which are kamma. This is like the heat. The present human body is like the match-stick, the new fetus, which might be a non-human fetus, is like the candle. When the conditions are right, consciousness arises in the new fetus. No soul is transferred, but there is a causal relationship between the two existences. In the case of rebirth, unlike in the simile, consciousness in one existence must cease before it can arise in the second existence.
Please note that just as the flames may be entirely different colours, sizes, temperatures, etc., in the first fuel and the second fuel, the same is true of the form that life takes before and after rebirth. To give a simple example: a female mouse may be reborn as a male elephant, or a Caucasian male may be reborn as an Asian female. It all depends on the mental process that is driven by kamma. One does not always get what one wants, but one always gets what one deserves.
Where To Sir?
Rebirth into the heavenly realms is spontaneous, as there is no gestation or fetal stage. Celestial beings are reborn with their subtle bodies fully developed. In the analogy of the flame, it would be like a gas flame rather than a candle flame.
Yes, kamma is the overriding factor that determines where rebirth takes place, but prayer or aspiration plays a significant role too. To give another simile. Suppose one were to arrive at an airport with sufficient money in one’s pocket to stay at the best hotel in town. If the taxi driver asked, “Where to, sir?” one might say, “Oh! It doesn’t matter. Take me to the nearest hotel.” The nearest hotel might be a bit of a dump, whilst the best hotel might be the other side of town. Kamma is like the money in one’s pocket, while aspiration is like what one says to the taxi driver.
If one arrives with only $25 in one’s pocket, one will have to say, “Take me to the cheapest guest house” otherwise when one gets to the five-star hotel, the taxi driver will take the $25 and the concierge will not even let one into the foyer.
Gestation (or incubation) is only necessary in the human and animal realms, where beings are born in the womb or in eggs. In the case of rebirth in celestial realms, and also in the lower realms of hungry ghosts, demons, and in hell, rebirth takes place spontaneously with a fully formed body created by kamma.
Beings in the realms of form (rūpa loka) are reborn there by the power of deep absorption (jhāna) and since there is no sex there, it makes little sense to refer to them as male. This is also the case with the formless realms (arūpa loka), where there in only mind and no matter.
The same could perhaps be said regarding the human fetus that has not yet developed sexual characteristics. It begs the question, Why are some acted upon by testosterone while others are not? However, we are getting into deep waters here beyond my knowledge of biology. According to my understanding, the sex is already determined at conception due to that particular being’s kamma and aspiration. However, it is possible that sex is not determined by the kamma that causes rebirth, but only by supportive kammas that bear fruit afterwards.
The kamma that causes rebirth is like the seed, supportive kammas that function thereafter are like the soil, water, fertiliser, and sunlight. Obstructive or counteractive kammas may also intervene resulting in miscarriage, deformities, or abortion These are like fungal infections, insects, flood, fire, or vermin, that may prevent a seed from developing into a full-grown plant.
Time to Move On
Kamma is the driving force that keeps us revolving in the cycle of rebirth (saṃsāra). Kamma is the Almighty creator. The Buddha fully understood the law of kamma and taught us how it works, but predicting its results is even more difficult than predicting the weather. The Buddha warned that to try to reason out the specific causes or results of kamma would lead to insanity. However, what we can do is understand the basic principles of kamma. Then we will avoid unwholesome kamma, cultivate wholesome kamma, and try to gain liberation from kamma.