Isn’t it irrational to believe things we cannot experience with our senses?
That is not being rational. To be rational means to use your reason, and you are not doing that. If you are going to limit your belief only to what you can detect with your senses, you are excluding a great deal of reality. The universe contains more than you can discover on your own.
If you depend only on what your eyes can see and nothing else, you are prone to error as well. Your eyes may tell you the sun rises and sets, but your reason (and your human faith in what astronomers, mathematicians, and physicists tell us) makes you realize the truth–the Earth moves around the sun.
There are many things, including spiritual things, that exist whether you have seen them or not. A person who declines to accept their existence is not working on the basis of sound reason, but on “blind faith,” and someone who insists nothing exists beyond what his senses can detect–particularly someone who rejects out of hand the supernatural–might be called out of sync with reality.
We recommend you read Frank Sheed’s best book, Theology and Sanity.
Despite the title, Theology and Sanity has nothing to do with psychiatry. Sheed said a man who rejects the supernatural is like a physician who rejects bacteria. You begin to think he isn’t all there. A physician who says bacteria aren’t real operates from prejudice, not science, and someone who says the supernatural isn’t real operates the same way.