——可溯至1512年的德国，早于马克思使用这个典故两个多世纪

　　　　　　　　　　——著名天文学家开普勒1610年就用这个典故捍卫他的占星观了

　　“倒洗澡水连孩子也倒掉”，在中国是一个经常使用的比喻。然而，这一说法的出处，中文网络一般认为源于马克思形容哲学家费尔巴哈批判另一位哲学家黑格尔的方式。

　　十九世纪德国有个哲学家叫黑格尔，他有一套唯心主义的思想，这是黑格尔的错误之处。但他讲的唯心主义道理中，包含着很丰富的辨证法因素，很能启发人的智慧，帮助人们正确的思维，这又是应该通过批判加以吸收的东西。 在他之后，同是德国的哲学家费尔巴哈，是一个唯物主义者，他对黑格尔唯心主义观点进行了有力的批判。他这么做是对的，但是，他在批判黑格尔唯心主义观点时，把黑格尔的辩证法思想也一慨否定了。

　　马克思使用“洗澡水”的比喻批评费尔巴哈像一个糊涂的老太婆，在给婴孩洗了澡后，把婴孩和脏水一块泼到门外去了。本意是指事物本身中存在的否定，不能机械地否定，而是辨证地否定。机械的否定，就是把事物本身全部消灭，就像那个糊涂的老太婆一样，把脏水和婴孩一起倒掉。

　　《咬文嚼字》2015年09期发表的《连同孩子一起倒掉的是“洗澡水”，而非“洗脚水”》认为“把洗澡水连同孩子一起倒掉”，意思是分不清精华与糟粕而全盘否定。这个俗语源于生活，流传很久，已无从考证其源头，大约是舶来品。”

　　据介绍，这个典故，列宁与鲁迅都在文章中使用过。鲁迅所用的原话或含义可能是，在往外泼洗澡水时，连同坐在浴盆中的婴儿一齐倒掉，这做法是最愚蠢的妇人也不取的。具体出自哪篇文章，我不太清楚。

　　然而，最早源头在哪里，可能确实不是很清楚，但书面出处明显早于马克思使用这个典故2个多世纪。据英文维基百科与英文词语词源的有关网页，这个典故最早可追溯至德国的一本书，使用时间为1512年。

　　据词源类网站介绍（https://www.wisegeek.com/what-are-the-origins-of-the-phrase-throw-the-baby-out-with-the-bathwater.htm），“throw the baby out with the bathwater”的最早时间虽然不很确定，但1600年时这个典故已相当普遍。天文学家开普勒也在那个时候使用过这个典故。

附1：https://en.wikipedia.org/wiki/Don%27t_throw_the_baby_out_with_the_bathwater）：

　　　　　　　　　　　　Don't throw the baby out with the bathwater 

　　The earliest record of this phrase is in 1512, in Narrenbeschwörung ( Appeal to Fools) by Thomas Murner; and this book includes a woodcut illustration showing a woman tossing a baby out with waste water. It is a common catchphrase in German, with examples of its use in work by Martin Luther, Johannes Kepler, Johann Wolfgang von Goethe,...

附2：https://en.wiktionary.org/wiki/throw_the_baby_out_with_the_bathwater

　　　　throw the baby out with the bathwater

Etymology

From a German proverb that dates to 1512. First recorded by Thomas Murner in his satire Narrenbeschwörung. First appeared in English when Thomas Carlyle translated it and used it in an 1849 essay on slavery.

附3：http://lishi.zhuixue.net/2016/0614/47529.html

http://www.cnki.com.cn/Article/CJFDTotal-YWJZ201509013.htm

　　　　　　　　　　　　连同孩子一起倒掉的是“洗澡水”，而非“洗脚水”

　　　　　　　　　　　　　　　　　　发布时间：2016-06-14 　

　　　　　　　　　　　　　　　　　　　　　　　蔡维藩

注：此文刊发于《咬文嚼字》 2015年09期

　　2015年3月27日《语言文字报》第2版头条《从阅读三功能看分层教学》一文说道：“不能因为分层教学有可能模式化，而‘洗脚水连同孩子一起倒掉’，忽视淡化甚至摒弃分层教学。”引语中“洗脚水”是“洗澡水”之误。

　　“把洗澡水连同孩子一起倒掉”，意思是分不清精华与糟粕而全盘否定。这个俗语源于生活，流传很久，已无从考证其源头，大约是舶来品。BBC英伦网英语教学频道收有地道英语“Throw the baby out with the baby bath water”，汉译是“把婴儿和洗澡水一起倒掉”。列宁说过：“他们反对形而上学（是恩格斯所说的形而上学，不是实证论者即休谟主义者所说的形而上学）的唯物主义，反对它的片面的‘机械性’，可是同时把小孩和水一起从浴盆里泼出去了。”（《唯物主义和经验批判主义》，《列宁选集》，人民出版社1960年4月第1版第268页）

　　结合生活实际，把孩子放在澡盆里，才有可能连同洗澡水一起倒掉；若孩子只是在盆里洗脚，是不大可能出现这样的失误的。

附4：https://www.phrases.org.uk/meanings/dont-throw-the-baby-out-with-the-bathwater.html

Don't throw the baby out with the bathwater

Other phrases about:

• Proverbs

What's the meaning of the phrase 'Don't throw the baby out with the bathwater'?

Don't discard something valuable along with something undesirable.

What's the origin of the phrase 'Don't throw the baby out with the bathwater'?

Proverbs are intended to pass on popular wisdom and are frequently expressed as warnings - 'don't count your chickens', 'don't look a gift horse in the mouth' and so on. 
Of all the 'don't do that'... proverbs this one seems the easiest to agree with.
To that list of don'ts we can add the odd-sounding 'don't throw the baby out with the bathwater'. Sadly, any discussion of the origin of this proverb has to refer to the nonsensical but apparently immortal email that circulates the Internet 'Life in the 1500s' (or 1600s, as some variants have it). One of the claims in one version of that mail is that "in medieval times" people shared scarce bathwater and by the time that the baby was bathed the water was so murky that the baby was in danger of being thrown out unseen. Complete twaddle, of course.

What is unusual about this phrase is that, quite by chance, the mischievous author of 'Life in the 1500s' hit on a correct date - the proverb did originate in the 1500s. 'Throw the baby out with the bathwater' is a German proverb and the earliest printed reference to it, in Thomas Murner’s satirical work Narrenbeschwörung (Appeal to Fools), dates from 1512. Murner wrote in German of course, but we hardly need a translator as he was good enough to include a woodcut illustrating the proverb. The expression was part of everyday German language from then onward (as 'Schüttet das Kind mit dem Bade aus') but didn't emerge in English until the 19th century. The Scottish philosopher and German scholar Thomas Carlyle was well acquainted with German proverbs and translated it in an essay denouncing slavery entitled Occasional Discourse on the N*gger Question (written in 1849 and published in 1853):

And if true, it is important for us, in reference to this Negro Question and some others. The Germans say, “you must empty-out the bathing-tub, but not the baby along with it.” Fling-out your dirty water with all zeal, and set it careering down the kennels; but try if you can to keep the little child!

附5：https://www.wisegeek.com/what-are-the-origins-of-the-phrase-throw-the-baby-out-with-the-bathwater.htm

　The phrase “throw the baby out with the bathwater” appears to be German in origin, and it essentially means that the good should not be discarded along with the bad due to inattention or haste. Before one gets a mental image of flying babies and dirty bathwater, it should be added that this term was always used as a metaphor to suggest that people should not race to hasty decisions, not that parents would actually throw their baby out.

　No one is quite sure when the Germans first started saying that one shouldn't throw the baby out with the bathwater, but by the 1600s, the term was common enough for it to be referenced by astronomer Johannes Kepler in a way which suggested that he assumed that his readers knew what he was talking about. From Germany, the slang term spread to France, and then into England. By 1853, Thomas Carlyle was mentioning the need to avoid tossing the baby out with the bathwater, and he also referenced the fact that the proverb was of German origin.

　One might reasonably wonder how it is that people could even imagine that someone could throw the baby out with the bathwater by accident. The explanation for this term lies in the fact that Europeans bathed infrequently after the Middle Ages, for a variety of reasons; many people, for example, thought that bathing was unhealthy, and avoided it except on rare occasions. When people did bathe, they filled a large tub with water heated on the stove, and the whole family took turns using it, with the oldest going first.

　By the time young children reached the bathtub, the water would be tepid, and rather dirty, thanks to the previous bathers. One can easily imagine an infant slipping into the water and becoming obscured by the muddy gloom, although since someone had to be present to bathe the infant, it is unlikely that the baby would have slipped entirely below the surface, or that someone would have dumped the baby out when emptying the tub, since most people keep track of the location of their babies. The image of tossing the cloudy contents of the bath without pulling the baby out first would have been compelling to Europeans living in this era, even if it never actually happened.

　This slang term references the idea that hasty decisions can sometimes result in disastrous consequences. Sometimes, it is necessary to take a break to find the good and the bad in a situation before making a choice about what to do; in other words, take the baby out of the tub so that you don't toss him or her away.

附6：http://onereed.com/books/keplers_astrology.php

 　　　Kepler's Astrology: The Baby, the Bathwater, and the Third Man in the Middle

　　　　　　　　　　　　　　　　　　　　　　Translated by Ken Negus
　　　　　　　　　　　　　　　　　　　　　　　　　Introduction and editor's notes by Valerie Vaughan

"Don't Throw the Baby Out with the Bath Water!"
These were Johannes Kepler's words of warning which he placed on the title page of his great defense of astrology published in 1610. Like most of Kepler's astrological writings, this book was never translated into English -- until now. After many years of research and preparation, Ken Negus and Valerie Vaughan have produced the first complete English translation of Kepler's Tertius Interveniens (pronounced "ter-she-us intervene-yens") -- "The Third Man in the Middle."

Kepler called himself a middleman because he was addressing his defense of astrology to extremists on both sides -- those who condemned astrology outright, and those who accepted everything about astrology (neither side using any critical thinking). Kepler's intention was to reform astrology -- to throw out the superstitions (the "bathwater"), while still preserving the valuable principles (the "baby").

Kepler is of course well known as a scientist, but few people know that he was a serious student and practitioner of astrology. Very few of Kepler's astrological writings have ever been translated (or even published at all), mainly due to the overwhelming academic prejudice against astrology, which has amounted more or less to censorship. Academic scholars who know almost nothing about the complex subject of astrology have continued for over 100 years to mis-represent Kepler's astrological work as worthless mysticism, "hogwash," and something he was "forced" to do to support himself financially. One respected authority even suggested that we would all have a better opinion of Kepler if he had burnt this (astrological) material. With this kind of bias expressed by translators and scholars, one has to wonder how "clean" their translations are. It is thus quite a momentous occasion when Kepler's primary work on astrology has been translated by an actual expert in the subject -- Ken Negus -- a retired Professor of German Literature at Rutgers University and the president of the Astrological Society of Princeton, NJ, since 1972.

附7：https://wordhistories.net/2018/11/23/throw-baby-bathwater/（这个网页的解释非常详细，但文字无法复制）