Origin of the phrase, ‘In necessariis unitas’

Like me, you’ve probably heard some variation of the phrase, “In essentials, unity; in non-essentials, liberty; in all things, charity.” It’s a translation of the Latin phrase, “In necessariis unitas, in dubitas libertas, in omnibus caritas.” Nineteenth-century church historian Philip Schaff calls it “the watchword of Christian peacemakers.”(1) The phrase is often attributed to the theologian St Augustine of Hippo (354-430),(2) but it sounds foreign to his style and is not found in his extant writings.(3)

Who, then, coined the phrase? No, it wasn’t Rick Warren, or that other memorable wordsmith, Donald Trump. In addition to Augustine, the phrase, or motto, has been variously attributed to the English cleric and theologian John Wesley (1703-1791), the English Puritan leader Richard Baxter (1615-91), the sometime Catholic, sometime Protestant writer Marco Antonio de Dominis (1560-1624), and the German Lutheran Reformer Philip Melanchthon (1497-1560).

In recent years the search for the source of the phrase has spawned quite a few blog posts, three of the best of which are here, here and here. In my judgment, the collective wisdom of book and blog identifies the most likely source as the obscure seventeenth-century orthodox Lutheran pastor and theologian Peter Meiderlin (aka Rupertus Meldenius, and Petrus Meldenius), writing in 1627. It appears that he died at Augsburg in 1651.

The original source must certainly predate 1679, when Richard Baxter finished writing a tract titled The True and Only Way of Concord of All the Christian Churches (4), in the preface of which he quotes a version of the phrase (see below). It is clear that he is reciting what appears to be a well-known quote, although it is unattributed.

Baxter then refers to Meldenius by name on page 25, and quotes the phrase. Philip Schaff explains this in detail, along with much more background information, on pages 650-653 of his volume referred to above. H.J.M. Nellen also confirms Rupertus Meldenius as a source, but posits an earlier source.(5) Baxter, and others who followed who were not merely quoting Baxter, presumably found the phrase in Meldenius’s work, Paranaenesis Votiva pro Pace Ecclesiae, published at Rottenberg in 1626, page 26.(6)

It is possible that Marco Antonio de Dominis used the phrase earlier, in 1617, and Meldenius quoted him, but I do not have convincing textual evidence for this.

Let me know if you find further evidence of the source of this excellent quote.


  1. Philip Schaff, History of the Christian Church (vol. 7; 2nd edition; New York: Charles Schribner’s Sons, 1910; repr. Grand Rapids: Eerdmans, 1960), 650.
  2. “Well-known theological saying of Augustine which is used as a principle for authentic ecumenism and as an antidote to theological controversy.” So says James T. Bretzke, SJ, in his otherwise fine resource, Consecrated Phrases: A Latin Theological Dictionary (third edition; Collegeville, MN: Liturgical Press, 2013), 105.
  3. Hugh P. Jones (ed.), Dictionary of Foreign Phrases and Classical Quotations (rev. edition; Edinburgh: John Grant, 1958), 58.
  4. Richard Baxter, The True and Only Way of Concord of All the Christian Churches (London: Thomas Parkhurst, Jonathan Robinson, and John Lawrence, 1707 [1680]).
  5. H.J.M. Nellen, “De zinspreuk, ‘in necessariis unitas, in non necessariis libertas, in utrisque caritas’,” Nederlands Archief voor Kerkgeschidenis 79 (1), 1999, 99–106.
  6. See also Carl Bertheau, “Meldenius, Rupertus,” in Samuel Macauley Jackson, VII (ed.), The New Schaff-Herzog Encyclopedia of Religious Knowledge (Grand Rapids: Baker Book House, 1968), 287.
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