That is hard to say.
In theory the witness of scripture could be seen as primary. But there is still the question of how one understands the meaning of scripture. So the other three can be seen as checks on the proper interpretation of scripture.
From another perspective, since the witness of the Holy Spirit is a direct witness from God, it could be seen as primary with the other three as a check to verify the validity of what is necessarily a subjective experience.
And in the Catholic tradition at least, the witness of the church, both historical and contemporary, would likely be seen as primary, with the others as cross-checks.