I have a monitor here.

I have three items around it.
#1. A water bottle.
#2. A coffee mug.
#3. A box of Keenex (r) brand tissues.

Can anyone tell me which item is CLOSEST to my monitor?

That's right. Without knowing where my monitor is, you cannot tell which item is closer to it.

The same goes for opinions and "The Truth".

You cannot tell if someone's opinion is closer to "The Truth" than someone else's without knowing what "The Truth" is.

And, if someone knows what "The Truth" is, then he doesn't have an "opinion". He has "The Truth".