You can't have your cake and eat it (too) is a popular English idiomatic proverb or figure of speech. Many people misunderstand the meanings of "have" and "eat" as used here but still understand the proverb in its entirety and intent and use it in this form. Some people feel this form of the proverb is incorrect and illogical and instead prefer "you can't eat your cake and have it (too)", which is in fact closer to the original form of the proverb (see further explanations below) but very rare today. Other rare variants use "keep" instead of "have".
The proverb literally means "you cannot both possess your cake and eat it". It can be used to say that one cannot or should not have or want more than one deserves or can handle, or that one cannot or should not try to have two incompatible things. The proverb's meaning is similar to the phrases "you can't have it both ways" and "you can't have the best of both worlds." Conversely, in the positive sense, it refers to "having it both ways" or "having the best of both worlds."
The order of the clauses in the saying has been the subject of some debate, and was even used in forensic linguistics (contributing to the identification and arrest of the so-called Unabomber).
An early recording of the phrase is in a letter on 14 March 1538 from Thomas, Duke of Norfolk to Thomas Cromwell, as "a man can not have his cake and eate his cake".
The phrase occurs with the clauses reversed in John Heywood's "A dialogue Conteinyng the Nomber in Effect of All the Prouerbes in the Englishe Tongue" from 1546, as "wolde you bothe eate your cake, and have your cake?". In John Davies' "Scourge of Folly" of 1611, the same order is used, as "A man cannot eat his cake and haue it stil." In Jonathan Swift's 1738 farce "Polite Conversation", the character Lady Answerall says "she cannot eat her cake and have her cake."
The order was reversed again in a posthumous adaptation of "Polite Conversation" in 1749, "Tittle Tattle; or, Taste A-la-Mode", as "And she cannot have her Cake and eat her Cake." From 1812 (R. C. Knopf's "Document Transcriptions of War of 1812" (1959) VI. 204) is a modern-sounding recording as "We cannot have our cake and eat it too."
Paul Brians, Professor of English at Washington State University, points out that perhaps a more logical or easier to understand version of this saying is, "You can’t eat your cake and have it too." Professor Brians writes that a common source of confusion about this idiom stems from the verb to have which in this case indicates that once eaten, keeping possession of the cake is no longer possible, seeing that it is in your stomach (and no longer exists as a cake).
Alternatively, the two verbs can be understood to represent a sequence of actions, so one can indeed "have" one's cake and then "eat" it. Consequently, the literal meaning of the reversed idiom doesn't match the metaphorical meaning. The phrase can also have specialized meaning in academic contexts; Classicist Katharina Volk of Columbia University has used the phrase to describe the development of poetic imagery in Latin didactic poetry, naming the principle behind the imagery's adoption and application the "have-one's-cake-and-eat-it-too principle".
Various expressions are used to convey similar idioms in other languages:
Bulgarian: И вълкът сит, и агнето цяло – Both the wolf is full, and the lamb is whole.
Bosnian: Ne možeš imati i jare i pare. You can't have both a lamb and money.
Czech: Aby se vlk nažral a koza zůstala celá – The wolf is full and the goat stayed whole.
Chinese: 又要马儿跑，又要马儿不吃草' (pinyin: Yòu yào mǎr pǎo, yòu yào mǎr bu chī cǎo.) – To want a horse that both runs fast and consumes no feed; or 魚與熊掌不可兼得 from Mencius – You cannot have both the fish and the bear's paw (as a rare delicacy) at the same time.
Danish: Man kan ikke både blæse og have mel i munden – You cannot both blow and have flour in your mouth.
Dutch: Je moet kiezen of delen – You have to choose or partition. This is based on Dutch civil law where in a derision of property one person divides the property in two parts and the other person chooses the part he likes most.
French: Vouloir le beurre et l'argent du beurre – to want the butter and the money from (selling) the butter. The idiom can be emphasized by adding French: et le sourire de la crémière (and the smile of the female buttermaker).
German: wasch' mich, aber mach mich nicht naß! – please wash me, but don't get me wet!.
Switzerland: Du chasch nit dr Füfer und s Weggli ha – you can't have the five cent coin and a Swiss bread roll.
Greek: Και την πίτα ολόκληρη και τον σκύλο χορτάτο – you want the entire pie and the dog full.
Hebrew: אי אפשר לאכול את העוגה ולהשאיר אותה שלמה – you can't eat the cake and keep it whole.
Hungarian: Olyan nincs, hogy a kecske is jól lakjon, és a káposzta is megmaradjon. – It is impossible that the goat has enough to eat and the cabbage remains as well. Also, Hungarian: Egy fenékkel nem lehet két lovat megülni. – It is impossible to ride two horses with one butt. (The meaning is similar to the Russian translation.)
Italian: Avere la botte piena e la moglie ubriaca – to have the barrel full and the wife drunk.
Nepal: दुवै हातमा लड्डु – having laddu (a sweet candy) in both your hands.
Papiamentu: Skohe of lag'i skohe – choose or let choose.
Persian: هم خر را خواستن و هم خرما را – wanting both the donkey and the sugar-dates.
Polish: Wilk syty i owca cała – The wolf is full, and the lamb [is] whole.
Portuguese: Querer ter sol na eira e chuva no nabal – Wanting the sun shine on the threshing floor, while it rains on the turnip field.
Romanian: Nu poți împăca și capra și varza – You can't reconcile the goat and the cabbage.
Russian: И рыбку съесть, и в воду не лезть – wanting to eat a fish without first catching it from the waters.
Slovene: Volk sit in koza cela - The wolf [is] full, and the lamb [is] whole.
Serbian: Не можеш да имаш и јаре и паре – You can't have both goatling and money.
Spanish: Querer estar en Misa y en procesión – wishing to be both at Mass and in the procession, and Spanish: estar en Misa y repicando (or Spanish: estar en Misa y tocar la campana – to be both at Mass and in the belfry, bell-ringing.
Argentina: Spanish: la chancha y los veinte – the pig and the twenties. (Comes from the old piggybanks for children that used to contain coins of 20 cents. The only way to get the coins was to break the piggybank open – hence the phrase. This can be emphasized by adding Spanish: y la máquina de hacer chorizos – and the machine to make sausage.
Tamil: மீசைக்கும் ஆசை கூழுக்கும் ஆசை – desire to have both the moustache and to drink the porridge.
Post at "The Phrase Finder", quoting Wise Words and Wives' Tales: The Origins, Meanings and Time-Honored Wisdom of Proverbs and Folk Sayings Olde and New and The Random House Dictionary of Popular Proverbs and Sayings.