Proofs
  The Nature of Faith
  Pascal's Wager
  The Will to Believe
  Non-propositional Faith
The Nature of Faith

Summary

Central to the debate between belief-in and belief-that is the concept of faith. To have faith in something is to have trust in it: "I have faith that you will pass your exams", "The England Cricket captain put his faith in the weatherman and elected to bat", and so on. However, faith does not necessarily imply knowledge and has in fact often been held up as a contrasting thing to it.

So, what do we mean by religious faith? St Thomas Aquinas argued that it lay somewhere between knowledge and opinion. For Aquinas, knowledge was beyond doubt, whilst opinion was a matter of choice. From this point of view the most certain things are logically necessary propositions - such as that "A is A" or "2+2=4".

However, if I say, "There must be life on some planet somewhere in the universe", it is only a matter of opinion. For such a thing to be true I would have to wait for technology to develop to a level where it could test this theory - up until then it is only probable (to whatever degree).

Faith, then, comes midway between these two extremes. I have no evidence for my opinion that there is life on some distant planet somewhere, but I may still choose to believe it despite the lack of evidence. If we view religious belief in this way we would define having faith as "choosing to believe that something is the case despite a lack of evidence" - or, "choosing to believe that the evidence for a thing being true is sufficient".