I've never seen air, but I know it exists (?)

I just ran into a pretty strange argument.  It is not the first time I have seen it, nor will it be the last.  The argument comes from a theist who argues that he knows his god exists even though it cannot be seen, much as he knows the air exists even though it cannot be seen.  This is a piss-poor argument.  Air can be detected in many ways, including visually, despite the claims of the theist.  Let me list some of the evidences that I have for the existence of air:

1. I can feel air's warmth or chill on my body, and quantify it with an instrument called a thermometer
2. I can measure air's pressure with an instrument called a barometer
3. I can feel the force of air's push against my body when the wind blows
4. I can see air pick up leaves and transport them to another location
5. I can see air shimmering as it rises off of a hot road in summer
6. I see how air causes the stars to twinkle in the night sky
7. I can witness how air can be used to generate useful power using a windmill
8. As a scuba diver, I can feel air compress inside my sinuses when I descend, and expand when I ascend
9. As a scuba diver, I can watch the bubbles air forms as I exhale underwater
10. As a scuba diver, I can feel air coming out of my tank when I turn on the valve
11. As a scuba diver, I can measure air's pressure in my tank with my submersible pressure gauge
12. As a scuba diver, I can see and feel air inflating my vest when I press the inflate button
13. I can hear air's vibrations when my ears detect sound
14. I can ride in an airplane which gets its lift from air interacting with the wings
15. I can sometimes look out the airplane window and actually see air rushing over the wing
16. I have ridden in a hot air balloon which generates its lift from the buoyancy of hot air over colder air
17. I can see how air changes the colour of the Sun during sunrise and sunset
18. I can see the effect air has on fire when I fan flames with my hands or an object
19. I can see the northern lights, caused by the interaction of energetic particles with air molecules
20. I can use my exhaled air to inflate a balloon 
21. I can see air surrounding Earth in photographs taken from space
22. As a skydiver, I can witness air slow my descent (vs. gravitational predictions) under a parachute

Can you think of more?  There are many, many pieces of objective* evidence, including visual evidence, for the existence of air.  What is the objective evidence for the existence of your god(s)?

*Despite many of these evidences being subjective to my senses, they are objective because almost all other people would agree with my experiences and describe them in the same way.