Reason and Faith

When should one use Reason and when should one use Faith? Are they mutually exclusive? Contradictorily, can one exist without the other?

Reason is using one belief to justify another, while Faith is believing in something without proper justification. In this fashion if one is to believe the Moon is made of cheese, they can do so based on Faith or Reason. If they do so based on Faith, it is because they are seeking to base their system of knowledge on something. If they do so based on reason, it is because they believe in something that causes them to believe in something else. But, when do we know when to use Faith and when to use Reason? Consider the Moon example--it might be wrong to use Faith in this example, for the very reason it would be of no use because Reason dictates that it is probably not so. However, as a scientist, having Faith the Moon is made of the same stuff of Earth is a proper use of Faith, even if it is not conclusive. Once the matter has been resolved, it is based on Reason--this belief of a material Moon goes off of the evidence (other held beliefs), such as the interpretation of its appearance through a telescope. Now I would like to point to a common misperception about Faith in this regard, what the scientist believes in the first case (Faith in a material Moon) is the same as the Christian doctrine of Faith. That a scientist believes the world to be of a certain manner, namely regular, is to have this sort of Faith. A Christian's Faith can cause belief in things that are not rational, even highly unlikely in some cases, but it is of the same order. The second type, and this may even be trivial at some point is the belief that one can understand the world through their senses. This is a lower order of Faith because it requires no leap, there is only what considers natural. The question is how do Reason and the higher order of Faith correlate? To begin with one needs Faith in some system, whether it be morality, rationality, mysticism, personality, or any other sort of mode of believing. Once that is established you can use that system to derive other truths using Reason (the interplay of those Reasons developed from Faith and Reason). Faith is absolute (until Reason disrupts it) and Reason refines it to the situation. However this is not fair to still a higher order of Faith, different from belief in the world or how it works. This is Faith in people, and is often stated as Christian Faith--the belief that scientists are doing their job or the Pope is looking out for our best interest. While this may be helpful, I'm not very certain on it, but what makes it higher order than the first, that the world is such and second that it can be understood as such, is that it suggests we can influence how it is understood as such. Faith is the engine and Reason the wheel, brake, and gas pedal.