As a result of the kind of question that I put towards people who try to convince me of the existence of a god/gods, I usually end up with them asking me about my religion. When I tell them that my religion doesn't demand faith, and is based on reasoning and logic, a common question that they ask me is of rebirth: How do I know that it actually happens? If you have not proof that it happens, isn't it called faith?
Before answering that question, I would like to point out again that my religion encourages me to question scripture and dogma. If it doesn't seem logical, do not accept it. If it seems to be rational and logical, then accept it. Now, I will try to explain from a logical way, why rebirth is acceptable to me. This is a personal thought process, it may or may not be acceptable to you [or even other Buddhists].
First, we have to define what it means by rebirth. As I understand it, the whole idea of reincarnation in the form that is expounded by the other major religions is not the same kind of rebirth as thought in Buddhism. In Buddhism, there is no concept of a personalised 'soul'. We're all made up of interchangeable constituent parts. Rebirth is merely a state transition.
As I'm an engineer, I usually try to use an engineering analogy. Makes it much easier for me to understand it. For simplicity, I will once again use the analogy of an engine that was not created. This engine, will serve it's function for a period of time. Due to wear and tear or some other factor, the engine will stop working one day. That's a mathematical certainty. Just like we do.
At this point, many possible things can happen to the engine. The engine can be left to rust, in which case the engine has transitioned into a new form, called scrap metal. After a while, it decomposes and we call it iron. It could also be broken apart, into what we call parts. It might be recycled into a million different metal toasters. It's even possible to recast it into a whole new engine.
So, if it's possible for this engine, to be converted from one form to another, why not us. If we look at ourselves long and hard enough, we will see that we're essentially similar to the engine, with different systems, sub-systems and parts working together. Granted, our cogs and gears are a little more complex, but we're essentially made up of nothing but a bunch of constituent parts that work together to perform a task.
Trying to see ourselves as 'special beings' that are different from anything else is vain delusion. Some people may say that we're different because we have a 'soul'. Now, show me some evidence of a 'soul' and I will think about the argument. Other people may say that we're different because we have a consciousness. Like I've said, we're more complicated than an engine, but if you look at it hard enough, a consciousness is also made up of layers, systems, sub-systems and parts. Just like how a piece of software works.
So, once this is established, the belief in rebirth is then no longer faith. It can be explained in a logical and rational manner. I have just given proof that rebirth can happen to an engine. So, why not us?