necessity in citing a source

[bookworm]

It appears that the criteria in citing a source are not that clear-cut sometimes, and academic people can have slightly different opinions on rare occasions.

When I was a student, I shared a newspaper clipping to an English teacher. The journalist wrote in the article: "There are no sellers when there are no buyers". I quoted the same in my essay without citing the source because I thought it was stating the obvious and not a unique saying. But my teacher underlined the sentence and wrote Source? beside it. Years later, I met another English teacher who agreed with me that there was no need to cite the source in that situation.

[Britta]

Well, this is different in different fields. Being a physicist myself makes my quotation life easy

I thought it was stating the obvious and not a unique saying.

Are not many famous quotes sort of "stating the obvious in a unique or creative way"? I think that this is what makes quotes go viral: it jumps at you and you realise that you knew it all along, only you didn't put it into a catching sentence.

[Bertha]

The key word in your explanation of how the quoted sentence was used is "quoted."  Anytime you quote someone or something used in another source, you should include a citation and for clarification, include an attribution.  For example, you could have written it as follows: John Smith wrote in his article that "there are no sellers without buyers" (citation).  Different documentation styles (MLA, APA, etc.) may handle the citation differently, too.  If you quote, you cite.  Simple.  Even if it's a common quotable quote.