The Essentials...

IN ESSENTIALS UNITY,

IN NON-ESSENTIALS LIBERTY,

IN ALL THINGS CHARITY.

On the Origin of the Sentence: "In necessariis unitas, in non-necessariis
(or, dubiis) libertas, in utrisque (or, omnibus) caritas."

This famous motto of Christian Irenics, which I have slightly modified in the text, is often falsely attributed to St. Augustin (whose creed would not allow it, though his heart might have approved of it), but is of much later origin. It appears for the first time in Germany, A.D. 1627 and 1628, among peaceful divines of the Lutheran and German Reformed churches, and found a hearty welcome among moderate divines In England.

The authorship has recently been traced to RUPERTUS MELDENIUS an otherwise unknown divine, and author of a remarkable tract in which the sentence first occurs.
...

Necessary dogmas are,

(1) articles of faith necessary to salvation;

(2) articles derived from clear testimonies of the Bible;

(3) articles decided by the whole church in a synod or symbol;

(4) articles held by all orthodox divines as necessary.

Not necessary, are dogmas

(1) not contained in the Bible;

(2) not belonging to the common inheritance of faith;

(3) not unanimously taught by theologians;

(4) left doubtful by grave divines;

(5) not tending to piety, charity, and edification.


http://www.georgetown.edu/faculty/jod/augustine/quote.html

http://www.ccel.org/ccel/schaff/hcc7.ii.vii.viii.html

Paul (Romans 15: 1-13) - "We who are strong ought to bear with the failings of the weak and not to please ourselves."

Charles Hodge comments here that "Since the points of difference are not essential, as the law of love, the example of Christ, and the honor of religion require concession, we who are fully persuaded of the unimportance of these things about which our weaker brothers are so scrupulous ought to act in accordance with their opinions and not behave just to please ourselves."


http://www.tulip.org/ccr/rom15a.htm