Ikkyu wrote:[b]How can a person prove that enlightenment exists,
There are no guarentees in Buddhism. Nobody is going to say "This is the one true way, believe blindly in it!". Buddha himself said not to blindly believe him, but to come and see for yourself. Only by putting the *practices* into practice for yourself and gaining experience with them will you be able to confirm or deny the reality of the Buddhist doctrine.
Ikkyu wrote:or that Bodhisattvas or Buddhas exist?
At first people take it on faith that a Buddha exists. This appears to contradict the previous statement. What is meant by this though is that you are taking it on faith that the Buddha nature exists in you and in all sentient beings, *but* you are not going to just let it be blind faith. You are going to believe, but you're also going to confirm it for yourself through practice. If you fail to do this, you just sell yourself short and your Buddhism will stay at the level of pure religion, and you will not gain many of the benefits that true Dharma practice offers. On the other hand if you choose to blindly deny the existence of Buddhas and Bodhisattvas because nobody is able to do a magic trick to cause your mind to stop being full of doubt, that's just as ignorant as someone who blindly believes but never confirms it for themselves.
Ikkyu wrote:What empirical evidence is there that any of the sutras, suttas, tantras and whatnot are true?
The experience of millions of Buddhists. The experience of thousands or tens of thousands or more individuals who have experienced various stages of Enlightenment for themselves, and confirmed it as reality for themselves. If you are looking for some kind of materialistic scientific proof, you won't find it. But Buddhism is the science of the mind, and its the best mind-science that this world has to offer. Even psychology pales in comparison.
Ikkyu wrote:I mean, most Buddhists are non-theistic. I too am a skeptic and was lead to believe that there isn't a personal god/sky-daddy watching over us, as the idea isn't supported by scientific fact. What real, hard evidence is there that bodhisattvas exist, that enlightenment is possibility or that rebirth can happen either? Outside of philosophical conjecture is it really possible to prove this? And if can't be proven, why become a monk and give your life to something that might not be true?
This is why you have to actually practice, and not merely study the Dharma. Without a teacher and steady practice you will just remain in doubt. If a Bodhisattva or Buddha walked right up to you and declared they were Enlightened, you will still remain in doubt. Even if they were able to display a perfect understanding of the Dharma and Buddha nature, existing in doubt and without any experience, it would just appear to be gibberish to you.
Ikkyu wrote:I'm not saying that these things aren't true, but before I take precepts I would like some evidence that Buddhism is actually something more than a dried up philosophy. I mean, claiming that you're a supremely enlightened individual is a pretty big deal, amirite? I'm considering the precepts but I'm still a skeptic. So prove me wrong.
Prove yourself wrong, its the only way.