Theory

Buddhism is an empirical philosophy. Buddha was very clear that we should judge the truth of any philosophy by its consequences. In the Kalama Sutra, he makes this particularly clear:

It is proper for you... to doubt, to be uncertain.... Do not go upon what has been acquired by repeated hearing; nor upon tradition; nor upon rumor; nor upon what is in a scripture; nor upon surmise; nor upon an axiom; nor upon specious reasoning; nor upon a bias towards a notion
that has been pondered over; nor upon another's seeming ability; nor upon the consideration, 'The monk is our teacher....'

What do you think...? Does greed appear in a man for his benefit or harm? Does hate appear in a man for his benefit or harm? Does delusion appear in a man for his benefit or harm?... being given to greed, hate, and delusion, and being overwhelmed and vanquished mentally by greed, hate, and delusion, this man takes life, steals, commits adultery, and tells lies; he prompts another too, to do likewise. Will that be long for his harm and ill?" ...

...when you yourselves know: 'These things are bad; these things are blamable; these things are censured by the wise; undertaken and observed, these things lead to harm and ill,' abandon them.

Buddhism is also a philosophy that is detached from theological considerations. Buddha, in fact, refused to answer questions concerning eternity and the afterlife. In the Kalama Sutra again, he notes how his philosophy helps whatever your beliefs about the afterlife may be:

The disciple... who has a hate-free mind, a malice-free mind, an undefiled mind, and a purified mind, is one by whom four solaces are found here and now.

Suppose there is a hereafter and there is a fruit, result, of deeds done well or ill. Then it is possible that at the dissolution of the body after death, I shall arise in the heavenly world, which is possessed of the state of bliss. This is the first solace...

Suppose there is no hereafter and there is no fruit, no result, of deeds done well or ill. Yet in this world, here and now, free from hatred, free from malice, safe and sound, and happy, I keep myself. This is the second solace...

Suppose evil results befall an evil-doer. I, however, think of doing evil to no one. Then, how can ill results affect me who do no evil deed? This is the third solace...

Suppose evil results do not befall an evil-doer. Then I see myself purified in any case. This is the fourth solace...