One thinks of the late Tom Lehrer:

  Your lips were like wine,
  If you'll pardon the simile;
  The music was fine
  If a bit Rudolph Friml-y.

(The Wienerschnitzel Waltz)

Since this is about language and similes, what about "You can't compare apples and oranges"? People say that frequently, but why in particular is that so?

I think you can compare any one thing to any other one thing. You can discuss what are their common features and what features they have that are not shared.

So it seems to me "Can't compare apples and oranges" is often used just as a polemic device, trying to attack your opponents by claiming what they are saying cannot be said.

I think it's more you shouldn't judge apples based on the criteria of how good it is at being an orange, and vice-versa.

Kind of like how you don't judge a fish on how well it climbs trees.

Who doesn't love them tree climbing fishies https://en.wikipedia.org/wiki/Mudskipper

It's always been like "you cannot compare values of different units" to me. Maybe we should start saying "you cannot compare kilograms to metres".

A kilogram is more than enough gasoline to move my car a meter.

`kg of fuel per metre` is division, not comparison. You can divide different units by each other. It isn't guaranteed to always make sense but it's very useful.

The result of division of two numbers is a comparison of those numbers.

The number of apples divided by the kilogram of oranges I have is a meaningless comparison and makes no sense, though.

If I had a nickel for every time I heard a comparison that nonsensical…

Hey, wait a minute-

The root of good faith conversation is that we don't latch on fuzzy meanings of words like "comparison" but try to understand which precise meaning should apply.

The result of subtraction is a difference. In my mind this is the most basic way to compare things. Subtraction of differing units is illegal.

The result of division is a quotient (day to day we say ratio). Division of different units is legal but not always practical.

Re: your deleted apples and oranges comments;

These aren't pure dimensionless numbers, they come with units of measure attached.

If there's need for good scalar try: https://en.wikipedia.org/wiki/Dimensional_analysis for https://www.sciencedirect.com/topics/chemistry/dimensionless...

The Czechs say that you can't compare the sky (or the heavens, depending on how you want to translate it) and bagpipes.

Probably because the word “contrast” has been subsumed by the word “compare”.

From thefreedictionary.com for contrast:

> contrast to examine differences; a striking exhibition of unlikeness: The contrast of styles intensified the impact of the paintings.

> Not to be confused with: compare – to liken; relate; examine similarities: compare the shades of blue

You can’t compare apples to oranges unless you talk about their similarities (round objects, fruits, etc). Similarities don’t offer any new value to the conversation of apples and oranges. You can “contrast” apples and oranges (red, orange, better, worse). Which adds new analysis to the topic.

It seems to me that "can't compare apples and oranges" is trying to say that you're using apple criteria to try to judge oranges. It's not that you can't compare apples and oranges, but you have to use fruit criteria to do so, not apple criteria or orange criteria.

So, to stop using similes: You can compare CPUs. You can compare memory chips. You can also compare memory chips and CPUs on, say, power consumption. But you can't compare memory chips to CPUs in terms of MIPS. If you try, then it's appropriate to accuse you of comparing apples to oranges.

Good point. If things exist in different "ontological categories" trying to evaluate which of them is "better" makes little sense.

But apples and oranges are both good food, so we can compare how much calories you get forjm them, or vitamins etc.

I think oranges and citrus generally is a weird variable because it’s hard to grow outside of tropical climates or advanced techniques:

https://en.wikipedia.org/wiki/Orangery

> In England, John Parkinson introduced the orangery to the readers of his Paradisus in Sole (1628), under the heading "Oranges". The trees might be planted against a brick wall and enclosed in winter with a plank shed covered with "cerecloth", a waxed precursor of tarpaulin, which must have been thought handsomer than the alternative:

> > For that purpose, some keep them in great square boxes, and lift them to and fro by iron hooks on the sides, or cause them to be rowled by trundels, or small wheeles under them, to place them in a house or close gallery.

So apples and oranges aren’t equally Veblen goods, which is another wrinkle. Apples can grow nearly anywhere, and do.

More context here:

https://www.gardenhistorygirl.co.uk/post/the-juicy-tale-of-t... | https://archive.is/l580N

Specific citrus fruits are sacred:

https://en.wikipedia.org/wiki/Etrog

I’ve never heard of apples being special outside of the Garden of Eden.

Interesting caption from that next to last link that perhaps goes against my point but is relevant to apples versus oranges comparisons:

> 'Hesperides' by Giovanni Battista Ferrari published in Rome,1646. Its full title meaning 'Hesperides, or, On the cultivation and use of the golden apple' (golden apples referring to citrus fruit)

Moreover if you chuck an apple and an orange in a mass spectrometer you will find that they are more or less exactly the same. I believe someone won an igNobel prize for that observation.

It seems to be a corruption of an older phrase comparing apples to oysters. Citation from 1670:

https://archive.org/details/bim_early-english-books-1641-170...

Apples and oysters are still things you can eat, but they're at least further apart than two fruits. The book also cites the similar expression "chalk and cheese".

The phrase originated from the Latin "non comparabilis" (not comparable) and gained popularity in English around the 1670s precisely because these fruits, while both round and sweet, have fundamentally different textures, flavors and growing conditions - making it a useful shorthand for comparing things with different essential qualities.