“Most of us can easily do two things at once; what’s all but impossible is to do one thing at once.”
The Complete Neurotic's Notebook (1981), Unclassified
Misattributed as Maxim 7, p. 13 https://books.google.com/books?id=GKFGAQAAMAAJ&pg=PA13&dq=%22To+do+two+things+at+once+is+to+do+neither.%22
Variant of:
Duos qui sequitur lepores neutrum capit
Who chases two rabbits catches neither.
A Dictionary of Quotations in most frequent Use, David Evans Macdonnel, 1797, quoted in The Monthly Review, 1798, p. 467 https://books.google.com/books?id=KYhPAAAAYAAJ&pg=PA467&dq=%22duos+qui+sequitur+lepores+neutrum+capit%22
Apparently of medieval or modern origin, not found in antiquity.
Misattributed
“Most of us can easily do two things at once; what’s all but impossible is to do one thing at once.”
The Complete Neurotic's Notebook (1981), Unclassified
Let's Be Frank (1957)
Context: It was extraordinary to be in two places at once, doing two different things — extraordinary, but not confusing. He merely had two bodies which were as integrated as his two hands had been.
14 April 1747
Letters to His Son on the Art of Becoming a Man of the World and a Gentleman (1774)
“Saying and doing are two things.”
Matthew 21.
Commentaries
“Practice isn't the thing you do once you're good. It's the thing you do that makes you good.”
Source: Outliers: The Story of Success
“When two do the same thing, it is not the same thing after all.”
Maxim 338
Sentences, The Moral Sayings of Publius Syrus, a Roman Slave
“The only two good things in life are doing mathematics and teaching it.”
La vie n'est bonne qu'à deux choses : à faire des mathématiques et à les professer.
quoted by François Arago in Notices biographiques, Volume 2 http://books.google.fr/books?pg=PA662&id=ZzNLAAAAYAAJ#v=onepage&q&f=false, 1854, p. 662.