The more common expression is "unity amid diversity." But that sounds a bit bland, conveying simply an abstract ideal that we would not know how to attain or that leaves us with all sorts of ideas without any animating spirit.
We need to be aware that the goal of unity, in whatever context it is taken, can be achieved precisely because of our differences and diversity of circumstances, situations, preferences, etc.
It is this variety and diversity that forms the basis for any effort toward unity. It is also what invites us and offers us the means to work for a unity that is not uniformity, a unity that can take on anything, reached not by any artificial means or controlled environment, but by the very things as they are in life, but approached and handled with a certain spirit.
We need to be aware of this need and duty, otherwise we would confine ourselves to an idea of unity that does not correspond to the real needs of people and the world in general. And given the increasingly complicated world we are having, we indeed have to learn this art and skill of attaining unity through diversity quickly.
We have to be most interested in unity because in the first place we are all human beings and we form one universal family in spite of our diversity of cultures, mentalities, lifestyles and other social, economic, historical circumstances, etc.
We have to learn how to weave one rich fabric, making use of all these different threads that come in a wide variety of colors and tints, of make and consistency. We have to learn how to orchestrate a deep pool of musical instruments to come out with beautiful symphony.
This is possible and practicable.
Another reason we have to be most interested in working for unity is, of course, because unity means a healthy life, or a system that is efficient and effective, fruitful and meaningful. We all deserve to enjoy this kind of life and system.
And the spirit proper to animate this effort of attaining unity through diversity is, to put it bluntly, the spirit of Christ. It is he who before his passion and death made that most fervent prayer to his Father that we be all one with him (ut unum sint) as he is also one with the Father and the Spirit.
St. Paul reiterates this truth when he said: "There is neither Jew nor Greek, there is neither bond nor free, there is neither male nor female. For you are all one in Christ Jesus." (Gal 3,28)
It is God who, as Creator of the universe and our most loving Father, is the foundation and purpose of our unity. No effort at unity would prosper without God at the center of it all.
And since we messed up with our sin the original unity and order, God sent his Son to recover that lost unity and enrich it even some more. The Son became man, and as 'the way, the truth, and the life,' taught us everything we need to know and showed us the way to attain unity not only through our legitimate diversity but also through our hostility against him and others.
All this he did by offering his life on the cross that summarized and completed all his preaching and redemptive work. It is the cross that would unite us in Christ, as he himself said: "If I be lifted up from the earth, I will draw all things to myself." (Jn 12,32)
It is the cross that also led to his resurrection that bore all the sins of man and everything that our sins cause. It is the cross that perpetuates the living redemptive work of Christ all through time.
Thus, the word he left us is always living and effective, the sacraments become effective channels of his grace, and the Church, in spite of its failing members, is truly the living Christ with us actively continuing with us his redemptive work.
It is him through the Church who teaches us all things about how to attain unity through diversity. We need to care for one another, attentive, mindful and thoughtful of everyone. We have to learn how to empathize and sympathize, unafraid to suffer for everyone.
We have to be experts in the art of dialogue, always having an attitude of openness, tolerance and patience. We have to live the social principles of the common good, solidarity and subsidiarity.
This is how we can achieve unity through the very diversity that marks our life here on earth!