This is a profound statement, xzins, and I love you for posting it.
To me, it's an if...then statement. Just like:
"If we forgive those who trespass against you, then Our Father will forgive us our trespasses",
He also says:
If the Church is in unity, then the world will know that You (the Father) sent Me."
That's how the Christians were defined in the beginning: "See these Christians, how they love one another."
The unity of Christians is either a "picture" of the unity of the Trinity, or, disunified, we are a "picture" of something else. Something menacing, disturbing, repellent and ugly.
Just a long way of saying... YOU ARE SO RIGHT ABOUT THAT!
That is another gem that comes out of that passage. Thank you.
Also, and I love this one, also from John 17: When the world sees that unity and love, it is so shocking, so unique, so other-worldly, that in amazement their mind jumps to "whatever the source of that is, I want some of it."
John 17:23b "Then the world will know that you sent me and have loved them even as you have loved me." World will know...you...
Our unity would prove God.
(Which is probably why the enemy fights so hard to foment disunity.)