Of course there is one truth. 1+1=2, Global warming either is or isn't real, gun control either does or doesn't reduce homicide rates, etc.
Aumann's Agreement Theorem suggests that two rational people can not disagree on a subject if they both fully understand all the evidence and arguments. All disagreements stem from some combination of misunderstanding, ignorance, or irrationality.
Then there is still only one truth and they can still come to an agreement on statements like "gun control is good if your goal is to reduce homicide rates" or "gun control is bad if your goal is to maximize personal freedom", etc.
Then it's not a matter of disagreement or coming to different conclusions, it's just having different values.
I think this works better. As someone said above, it comes down to trade offs. Arguing a point with a specific goal to work towards leads to better discussions than trying to answer questions like: "is x good or bad?"
Aumann's Agreement Theorem suggests that two rational people can not disagree on a subject if they both fully understand all the evidence and arguments. All disagreements stem from some combination of misunderstanding, ignorance, or irrationality.