I think that love is the realization of unity beyond any intellectual understanding. Unity already exists, but we only realize it when we love.
The Bible says: "And thou shalt love the Lord thy God with all thy heart, and with all thy soul, and with all thy mind, and with all thy strength: this is the first commandment."
Jesus says: "I and my Father are one".
Nothing more to add.
Love is unity. I agree, it's very simple. :)