In the current Idea Email, we explore one of Peter Drucker’s most compelling lessons regarding the reason any business exists. (Spoiler alert: It’s customers.)

In examining the dog-eared copy of the Hammock library’s The Essential Drucker, we were reminded of all the great insights he shared over his 60-year career. We were also struck by how many quotes attributed to him for which we can’t find the original source.

But still, he said (and maybe said) some things we really love.

Here are four that we can actually cite where Drucker said or wrote the quotation:

• “The aim of marketing is to know and understand the customer so well the product or service fits him and sells itself.“ (The Essential Drucker)
•  “The aim of marketing is to make selling superfluous.” (The Essential Drucker)*
• “Every enterprise is a learning and teaching institution. Training and development must be built into it on all levels—training and development that never stop.” (The Essential Drucker)
•  “The entrepreneur always searches for change, responds to it, and exploits it as an opportunity.” (Innovation and Entrepreneurship: Practice and Principles)

As an addendum, here are two quotes attributed to Drucker in hundreds of books and articles, and that certainly sound like Drucker, but that our fact-checkers can’t verify (in the time we provided them) where and when exactly, or even if, he said or wrote them.

• “The most important thing in communication is to hear what isn’t being said.”
• “The best way to predict the future is to create it.“

Bonus link: The Drucker Institute’s “Drucker Sampler,” links to some of his writings found online.

*We’ve seen this quoted by some very influential authors and “experts” as, “The aim of marketing is to make selling unnecessary,” but the version using the word “superfluous” is the one we can attribute directly to Drucker.