In terms of evidence, God's Holy Spirit is what the spiritually blind would see if they were not spiritually blind. Explaining what it is, is like explaining the color red to a person born blind.
But, you can describe the color red to a blind person and describe real real things that produce the color red. You can also describe it in scientific terms. You can't do any of that with holy spirit. Indeed, all you can do is avoid discussing it in a way that would put you on the spot of having to describe it.
To someone that sees, no need to look for an explanation.
That's called willful ignorance.