One philisophical principle is that in a set of hypotheses, the one with less assumptions should be validated. Most of my friends think that materialism is the worldview with the least assumptions since it only requires that we assume the physical world can be perceived, measured and understood by our human senses. These materialist friends say that the pursuit of spiritual things for the purpose of life is only a way for our consciousness to make us feel beter to live in a very objective world. How can I prove that the spiritual world is as real as the physical world and not just someting we “assumed” is real?
You are describing what is known as Ockham’s razor which was first proposed by William of Ockham in the 13th century. It is a common sense principle, not a law. Even Ockham never used it to “prove” anything, but simply proposed that in the lack of other reason to choose it is helpful. It was used eventually to remove supernatural explanations of the physical world by scientists such as Isaac Newton. Whether this principle can be used to decide which is the best world view is a dubious proposition. The best world view is the one which can properly explain reality, not the simplest one. Besides, it is not clear that naturalism has fewer assumptions. Naturalism assumes that unchanging natural laws exist, that all phemonena can be explained by these natural laws, that the universe in understandable by human beings and that the universe can be described by mathematics. Biblical theism requires the assumption thatthe universe was created by a Creator, that there are parallel spiritual and physical worlds, and that the Creator of both is a personal God. Which has more assumptions? I think they are about equal.
As I said in my presentation, the question is which set of assumptions best explains what we know about reality. I believe I showed that naturalism does a much poorer job of explaining reality. For example, it cannot explain why anything exists at all. It cannot explain why the universe appears so well “tuned” for life to exist. It cannot explain how self-aware beings emerged from a purely physical world. It cannot explain why all or virtually all humans are inherenty convinced that justice, love, and moral truth are real, not mere epiphenomena. It cannot explain how life, with its vast amount of energy, emerged from randomly arranged molecules. It cannot explain why there are dozens of prophecies of the Messiah in the Old Testament are fulfilled in Jesus. It cannot explain why Jesus was raised from the dead on the third day. There is a vast array of facts about the universe that naturalism/materialism cannot explain but which biblical theism can explain.
Be aware that this does not amount to “proof” that spiritual things are real. By their very nature, we cannot “prove”, as in a mathematical proof, the existence of God or of spiritual reality, but what we can do is show that this assumption is far more consistent with reality as we know it than materialism. That is good enough for me. I believe that it requires an almost supernatural level of faith to believe in the discredited assumptions of naturalism.
Let me know is this response is sufficient.