Hmm, not sure. I believe, as surely as if it were fact, that if an object such as a rock is dropped from a height above the ground, it will always fall towards the centre of the earth.
I believe this because I've never seen any (non-aerodynamic) object do otherwise and nor have any human beings in all of history. Isn't it observation that compels us to accept such things as fact, rather than mere 'faith'?
You cannot know anything unless you have accepted by faith, some things are true that you believe to be so. To think and understand the universe around you, your belief you are capable of doing that must be accepted on faith, the truths you accept are just that, have to be believed as well. To do science, the universe must be mathematically comprehensible to make predictions, and the foundation for all of these beliefs is due to?