I used to, until the Loch Ness Monster was outed as a fraud And you know how there used to be lots of bad, grainy, black & white photos of ghosts, UFOs, Big Foot, etc.? Well, now that everyone has a digital / video camera that can take decent pictures, the number of sightings have gone waaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaay down. Except for this one . . . http://imgur.com/Dvbl6
Yup I believe in them. IMO, still there are a lot of things which can not be seen but still they exist.
If you can see the earth's atmosphere in this picture you have seen air. "Air" is not something constant and can consist of various different molecules. Most of these molecules are not absorbing much ligh, therefore they appear to be transparrent for our eyes. However, when you compare almost nothing (space) to air you will see the difference and hence you will see air. Air mainly consists of a lot of different gases such as: molecular nitrogen, molecular oxygen, argon, methane, krypton, hydrogen, nitrous oxide, xenon and many more. These are found in various concentrations depending on your location. Fun facts: You can freeze air if you lower the temperature enough so that every molecule reaches its set point to go from gas to solid. Since air is mainly consisting of nitrogen, oxygen and argon you would need a minimum of about −370 °F to freeze all of these. However, depending on all the other impurities in the air it will most likely take even more to freeze it all. And the conclusion of this is that you will be able to see air with your naked eyes in close distance! It will most likely look like liquid nitrogen. I hope you learned something from this.
Oh right, I've learned that we can see these transparent gases as what you've said. They are merely reflections pretty much the same as how you look at water. You see water since it shows a reflection but without those, you wont be able to see something that is transparent. Then again, you see what you see and you believe what you want to believe.
Never mind then. I thought that when you said "you believe what you want to believe" that you meant that I was believing something untrue. Since the title is "Do you believe in things that you never seen?". If not then sorry. =)