Is this another way of asking whether belief in the existence of God must be irrational in light of God's intangibility? If so, I would answer No. There are many things that I cannot touch in whose existence I believe. For instance, I believe in the existence of Mars, but I'll never touch it. You might think that's a bad example because, while I can't actually touch Mars, I could in principle touch it: in theory, I could build a space ship that will bring me to Mars. God, on the other hand, seems to be something that I couldn't even in principle touch: according to many, God simply isn't located anywhere in the physical universe. But don't we believe in the existence of intangible things even in that stronger sense of "intangible"? For instance, most of us believe that the Equator exists, but it's not tangible (you can't trip over the Equator). Or, to take Richard's example, we all believe that the play A Comedy of Errors exists, even though it can't be touched, ripped up, or burned. Or finally, most of us think that numbers (like the number 8) exist though they don't seem to be at all located in the physical realm. So if one is irrational to believe in God's existence, that's not because God is something intangible.

Or perhaps you meant to be asking whether it's irrational to believe in an intangible God's existence on the basis of no evidence. If a person thinks the answer to that question is Yes, then God's intangibility again seems irrelevant: that person would likewise hold that it's irrational to believe in a tangible object's existence if one had no evidence at all for it. If there is irrationality here, its source is our lack of evidence and not the intangibility of the being that is believed to exist.