The true opposite of faith is not doubt.

That’s like saying “exercise is the opposite of fat”

No.  The opposite of exercise is sitting around and being lazy.

Faith is the bridge we use to cross over the unknown and the unseen into belief.

Without doubt there is no need for faith.

The true opposite of faith is fear.

Fear gives in to the doubt, just as laziness gives in to the fat.

Faith overcomes it.