When it comes to faith there are two kinds of people – those who understand and embrace the fact that faith of some kind is inevitable and those who try to dodge this ineluctable primordial datum.
We cannot know completely. Kurt Gödel demonstrated that even the basic principles of a mathematical system while true cannot be proved to be true. This is his incompleteness theorem. Gödel exploded the myth of the possibility of perfect knowledge about anything. If even a mathematical system must be taken on faith at certain level, is there anything we can know completely? No there is not. Faith is inevitable. Deny that fact and live a life of blinkered illusion, or embrace it and live in the light of truth, however incompletely we can apprehend it.