Argumentum ad ignorantiam

The argumentum ad ignorantiam (also known as the argument from ignorance or argument from (personal) incredulity) is a logical fallacy wherein the speaker claims that because a subject is not well understood, either by the speaker or by others, it cannot be true.

Apologetics
The argumentum ad ignorantiam is commonly used as a proof of the existence of God. The argument goes something like this:
 * 1) Gee, this sure is a big, complicated world.
 * 2) I don't see how it could have come into existence without an intelligence behind it.
 * 3) Therefore God exists.

This argument is also used to dismiss the possibility of biological evolution in this fashion:
 * 1) Evolution says that people just came into existence by chance.
 * 2) I cannot see how this is possible.
 * 3) Evolution must be false.

Irreducible complexity is based on the argument from ignorance.

Counter-apologetics
The argument from ignorance is, at heart, an Enthymeme, a syllogism with an unstated premise: (unstated premise highlighted.)
 * 1) I don't understand how x could have happened.
 * 2) Anything I don't understand is caused by God.
 * 3) Therefore, God caused x.

Sometimes a subject such as evolution is not understood by the speaker but may be well understood by many others, such as scientists. Of course, evolution is not a theory of chance, and has well established mechanisms underlying it.

Even when a subject is not well understood (i.e., the origin of the universe), that is not sufficient grounds for assuming an unproven answer like "God did it". Since the "explanation" of God is more complex than the entities that are purportedly explained by God, introducing God without evidence is simply begging the question.

There is a time where people need to understand that there are certain things that we currently do not possess the technology to know about. This is where the dreaded truth must come in - I don't know.