One, yet we differ

As we read The Quran, it is increasingly clear that the divisions on the basis of religion are human-made. In the Book's 42nd chapter, the following verses explain the phenomenon.

11. (He is) the Creator
Of the heavens and
The earth: He has made
For you pairs
From among yourselves,
And pairs among cattle:
By this means does He
Multiply you: there is nothing
Whatever like unto Him,
And He is the One
That hears and sees.

12. To Him belong the keys
Of the heavens and the earth:
He enlarges and restricts
The Sustenance to whom
He will: for He knows
Full well all things.

13. The same religion has He
Established for you as that
Which He enjoined on Noah-
The which We have sent
By inspiration to thee-
And that which We enjoined
On Abraham, Moses and Jesus:
Namely, that ye should remain
Steadfast in Religion, and make
No divisions therein:
To those who worship
Other things than God,
Hard is the (way)
To which thou callest them.
God chooses to Himself
Those whom He pleases,
And guides to Himself
Those who turn (to Him).

14. And they became divided
Only after knowledge
Reached them, - being insolent to
One another.
Had it not been
For a word that
Went forth before
From thy Lord,
(Tending) to a Term appointed,
The matter would have
Been settled between them:
But truly those who have
Inherited the Book after them
Are in suspicious (disquieting)
Doubt concerning it.

15. Now then, for that (reason),
Call (them to the Faith),
And stand steadfast
As thou art commanded,
Nor follow thou their vain
Desires; but say; "I believe
In whatever Book
God has sent down;
And I am commanded
To judge justly between you.
God is our Lord
And your Lord! For us
(Is the responsibility for)
Our deeds, and for you
For your deeds. There is
No contention between us
And you. God will
Bring us together,
And to Him is
(Our) final goal.