when is an assumption not a presumption?

Es­ti­mated reading time is 4 min­utes.

I AS­SUME THAT MOST OF US dare to pre­sume when we should be merely as­suming! Just the other day one of my friends drifted into dis­cussing the dif­fer­ence be­tween ‘as­sume’ and ‘pre­sume’ and be­fore ei­ther of us could look it up and find out the dif­fer­ence we were both called to other du­ties and there the con­ver­sa­tion rested until now be­cause I wanna know once and for all when is an as­sump­tion not a pre­sump­tion! 1

First I used Merriam-Webster On­line. Books with the MW trade­mark have been rea­son­ably trust­worthy since 1843 when George and Charles Mer­riam bought the rights to An Amer­ican Dic­tio­nary of the Eng­lish Lan­guage from the Noah Web­ster estate.

•  Ac­cording to MW, as­sume means “to think that some­thing is true or prob­ably true without knowing that it is true.”

•  Ac­cording to MW, pre­sume means “to think that (some­thing) is true without knowing that it is true.”



But! They both have the same definition!

(Why the one has one word in paren­theses is prob­ably known only to the hoariest of MW’s lexicographers.)



There is a second type of as­sump­tion, most closely iden­ti­fied with the Catholic Church: “The As­sump­tion of the Blessed Virgin Mary into Heaven is a de­fined dogma of the Catholic Church. The Feast of the As­sump­tion com­mem­o­rates the death of Mary and her bodily as­sump­tion into Heaven.” I found this en­graving on the web­site for The Cathe­dral of the Holy Family of Nazareth of Tulsa, Ok­la­homa. Alas, the artist is not credited.

To take for granted

So I turned to The Free Dic­tio­nary, an Amer­ican on­line com­bined dic­tio­nary, and en­cy­clo­pedia that de­rives its ex­pla­na­tions by cross-referencing the Amer­ican Her­itage Dic­tio­nary of the Eng­lish Lan­guage, the Co­lumbia En­cy­clo­pedia, the Com­puter Desktop En­cy­clo­pedia, the Hutchinson En­cy­clo­pedia, Wikipedia, and Acronym Finder, along with sev­eral spe­cialist dic­tio­naries (such as fi­nan­cial and legal).

•  Ac­cording to the FD, as­sume means “to take for granted; suppose.”

•  Ac­cording to the FD, pre­sume means, “to take for granted as being true in the ab­sence of proof to the contrary.”

So, ac­cording to the two dic­tio­naries that I refer to when on­line, there is es­sen­tially no dif­fer­ence be­tween the de­f­i­n­i­tions of the two words. But that is tech­ni­cally not so says the Gram­marist:

As­sume and pre­sume both mean to take some­thing for granted as true (among their many other de­f­i­n­i­tions). The dif­fer­ence is in the de­gree of cer­tainty. A pre­sump­tion is usu­ally more au­thor­i­ta­tive than an as­sump­tion. To pre­sume is to make an in­formed guess based on rea­son­able ev­i­dence, while to as­sume is to make a guess based on little or no ev­i­dence.” 2



On No­vember 10, 1871, Amer­ican Henry Morton Stanley made The Most Fa­mous Pre­sump­tion in Western His­tory when he greeted Scot­tish med­ical mis­sionary David Liv­ing­stone with the ques­tion, “Dr. Liv­ing­stone, I pre­sume?” Liv­ing­stone was a na­tional hero in Britain but hadn’t been heard from in six years at the time of this meeting. Stanley had been sent to find him by the New York Herald news­paper in 1869, and it took the in­trepid in­ves­tiga­tive jour­nalist two years be­fore he lo­cated the man in the town of Ujiji on the shores of Lake Tanganyika. 

When you assume

This I like: a vari­a­tion in theme, more or less. Most of the com­ments that fol­lowed the Gram­marist’s ex­pla­na­tion ei­ther con­curred with that ex­pla­na­tion or ex­pressed ap­pre­ci­a­tion for having a line drawn be­tween the two words. Sev­eral rea­son­able state­ments follow in the Com­ments sec­tion; my fave is from ‘Dash’:

“When you as­sume, you usu­ally make an ass out of u and me. That’s ex­actly what hap­pens when you don’t have enough information/evidence to make a presumption.”

I am con­tent with this ex­pla­na­tion, but for the sake of my more scrupu­lous readers, I pur­sued an­other ex­pla­na­tion, this time from the Ox­ford Dic­tio­naries on Lan­guage Mat­ters:

“In common usage, both as­sume and pre­sume can mean ‘sup­pose’ and are often in­ter­change­able in this meaning. How­ever, tech­ni­cally there is a subtle dif­fer­ence be­tween the two where pre­sume is to “sup­pose to be the case on the basis of prob­a­bility.” As­sume on the other hand is to sup­pose to be the case without proof.”

I began this piece for my “Strunk­and­whiten It” cat­e­gory as­suming that I would reach some con­clu­sion that sat­is­fied my cu­riosity and that of most readers. I pre­sume that I have:

•  All pre­sump­tions are as­sump­tions; only the better breed of as­sump­tion is a presumption.

•  You may as­sume any time you like and not look too foolish (as long as you have some­thing fac­tual to go by), but you’d better have more than an as­sump­tion to make a presumption.

•  Good luck ex­plaining the dif­fer­ence to those among us who think opinion is paramount.

Nothing more deceptive

“There is nothing more de­cep­tive than an ob­vious fact.” Sher­lock Holmes said that.

“Your as­sump­tions are your win­dows on the world. Scrub them off every once in a while, or the light won’t come in.” Isaac Asimov said that. 4

“Never make no f*cking as­sump­tions!” I said that.


Jesus Mary ChurchOfTheAssumption 1000

HEADER IMAGE: The photo at the top of this page was found on the (now ap­par­ently de­funct) Trover site. It is of the ceiling of the Church of the As­sump­tion (also known as Mary’s Tomb) in Jerusalem.



1   After all, never having to say you’re sorry is why Grom­mett, through his dis­ciple Al Gore, gave us the Internet!

2   When forming a pre­sump­tion, a little au­thor­i­ta­tive backing helps to dif­fer­en­tiate it from a mere as­sump­tion, and the word au­thor­i­ta­tive has a meaning. De­spite what our con­ser­v­a­tive brethren think, it does not mean “someone who shares my opinions.”

3   Isn’t “Dr. Liv­ing­stone, I pre­sume?” a ques­tion (the first two words) within a state­ment? Stanley is stating to Liv­ing­stone that he is pre­suming that he is Liv­ing­stone, so the four words do not form a ques­tion, but a de­c­la­ra­tion. Shouldn’t it be prop­erly punc­tu­ated as, “Dr. Liv­ing­stone? I presume.”

4   For more, Goodreads has an­other 157 state­ments on the fool­ish­ness of as­suming much of any­thing. (Um, you won’t find my state­ment there.)




5 thoughts on “when is an assumption not a presumption?”

  1. Re. Foot­notes 3 and 4: As­sume nothing.

    Foot­note 5: I thought it was an il­lus­tra­tion from Dan­te’s “In­ferno”!

    And, the whole thing goes round’n round. Paul Simon said it best, “The greatest story ever told.”


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