If you talk about knowledge, you talk about justified true believe. That means for knowledge to be knowledge you have to justify this knowledge with reasons. For example people have walked on the moon. Most of the people believe although there is no real justification for that. That's why we say that is believe. There are nine reasons for the justification.
Authority, Faith Logic, Intuition, Memory, Sense perception, Consensus Gentium, Self-awareness and Revelation.
Knowledge is classified by four characteristics. All of these characteristics must be met before one can make the statement "I know that p." P being any piece of propositional knowledge.
1. p must be true,
2. I must believe that p,
3. p must be justified by good reasons, and
4. There is no evidence to refute p.
Galileo for example based his attitude on the position of the Church Fathers, who claimed that clarifying the problems of the visible world of the senses was not a matter for the Church.
Such problems properly belong to the realm of changing and uncertain human knowledge, and must not be confused with Divine knowledge, given to humans in Revelation through Scripture. Theories based on human knowledge may prove wrong, and then there is a danger that the faithful may think that the tenets of their faith are also untrue. For this reason, the Catholic Church endeavored to refrain from deciding on problems of natural philosophy.
Another example for faith is in ancient Greece a few people were heliocentrists. They believed, that the earth revolves around the sun (which turned out to be a true belief), they had reasons for their belief, but not enough evidence to know that the earth went around the sun: at that time it seemed more evident, that the sun revolved around the...