In some ways I agree with Insanity X, spirituality has become a go to word for anyone who wants to make a point about what they believe yet can not prove. For me it is not a requirement of God that I have to nor need to prove His existence, what is required to be spiritual is having an ear for God and living the truth He places in my life, actually I believe that is a requirement for all Christians. So, when I use the word spiritual, I'm not trying to prove anything other than I listen to God and try to live as He desires, which mostly I fail at.
God loves those who believe and those who do not and the same goes for me, you have no choice in this matter. That puts the matter of total free will to rest.