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. The argument is a form of non sequitur.
Someone using the argument from ignorance will generally claim that either
- They don't know how an argument could be false, therefore it must be true.
- They don't know how an argument could be true, therefore it must be false.
- Since scientists cannot prove that global warming will occur, it probably won't. 
"There will never be an Isaac Newton for a blade of grass."
Use in apologetics
- Main Article: God of the gaps
The argumentum ad ignorantiam is commonly used as a proof of the existence of God. A God of the gaps argument is one that argues that since some phenomenon is unexplained, it must be due to God. It is also a form of non sequitur, since the hand of God is posited without proof and often with complete disregard to other possible explanations.
It also features in many other popular apologetic arguments, including:
- "This a homage is rendered to the sacred seal [of obscurity], which the Almighty has set upon each of his works. "