i do not intend a theological discussion as such, but then in my mind the truth is about god. jesus said he was the truth, so any truth comes from god, for he created all there is.
there are two kinds of servants. there are slaves -those who serve because they have to, and there are bond servants - those who serve because they want to. because of our condition as humans on earth, we must serve someone. therefore all that is left for us to exercise our free will on is the "who" and the "how". there is another category, but they are quite rare.
one can serve the flesh or the spirit. serving the flesh reaps death. serving the spirit reaps life. it is that simple.