Faith is not possible without knowledge or grace, but it is possible with only one of the two, when the other is lacking.
Infants, who do not possess knowledge, receive the gift of supernatural faith when they receive grace, at baptism. The state of grace, when infused into the soul, brings with it supernatural faith, hope, and charity. Even when intellectual knowledge is lacking (for those without the use of reason), faith is present when the soul is in the state of grace.
To those who have the use of reason (adults, etc.), faith requires the intellectual assent to the truths revealed by God. If a person knowingly rejects any truth revealed by God (any dogma of the faith), they loose all supernatural faith. But faith is possible without grace, because a person in mortal sin, for example, may still believe and thus have faith.
I’m not sure how clear that explanation was. St. Thomas has an entire section dealing with this issue. You can probably locate it by doing a google search.