Learn English – what does “lost a shilling and found a penny” mean

I'm not 100% sure, but maybe it's the valid argument form called "Modus ponens". If one thing (A) is true, then the other thing (B) will also be true.

Put in a logical form:

If A, then B

A

therefore B

For example: If it's Monday today, Sarah has to go to work

It is Monday today

Therefore Sarah has to go to work

I think that kind of logic might be, what Carroll was trying to explain.

"If it was so, it might be and if it were so, it would be; but as it isn't, it ain't. That's logic."

Translation:

If it was A, it might be B, if it were A, it would be B, but it isn't A then it ain't B

But maybe the last part "but as it isn't, it ain't" is actually Modus Tollens:

If A, then B

Not B

Therefore not A

So the last part (but as it isn't, it ain't) might be translated to:

But it isnt B, then it ain't A

If the latter is true, then the logic explained is Modus Tollens instead of Modus Ponens

I hope I didn't confuse you, and that you're satisfied with the answer :)

The set phrases "a few choice words" and "some choice words" have a more interesting past than I had imagined. Originally, the wording was used to indicate an especially pleasing bouquet of words, as, for example, in this instance from Vernon Lushington, "On Learning by Heart," reproduced in Class-Book of English Poetry (1866):

For those, in particular, whose leisure time is short, and precious as scant rations to beleaguered men, I believe there could not be a better expenditure of time than deliberately giving an occasional hour—it requires no more—to committing to memory chosen passages from great authors. If the mind were thus daily nourished with a few choice words of the best English poets and writers; if the habit of learning by heart were to become so general, that, as a matter of course, any person presuming to be educated amongst us might be expected to be equipped with a few good pieces,—I believe it would lead , far more than the mere sound of it suggests, to the diffusion of the best kind of literature, and the right appreciation of it, and men would not long rest satisfied with knowing a few stock pieces. ....

From M. de Betham-Edwards, The Sylvestres, serialized in Good Words for 1871 (1871):

Had the history of this gold chain been clearly made out, Ingaretha was certainly the original owner of it; but, in Monsieur Sylvestre's eyes, it mattered little how he came by a thing, so long as he had the pleasure of giving it away, and consecrating it by a few choice words, a hand-clasp, or, better still, if circumstances allowed, a kiss.

And from "The Books of 1884," in The Publisher's Weekly (January 31, 1885):

The late Dr. Ewer's sermons were issued in book-form, with the title "Sanctity and Other Sermons;" a selection of Talmage's most important sermons is embraced in the "Brooklyn Tabernacle ;" and some choice words of Beecher's in "Comforting Thoughts." Savage's "Beliefs About the Bible" is a Unitarian's inquiry into the divine origin of the Book.

But at some point, English speakers latched onto the expression as an ironical or euphemistic way to refer to naughty, harsh, denunciatory, brazen, or otherwise unsuitable-for-polite-company words. Thus, even as early as Ruth Sheldon, Scraps (1898), we have this instance:

A little boy of four, who had been out to play with older boys, and had picked up some choice words, said as his mother put him into his bath, "Jesus Christ, this water's hot!"

And likewise from Bill Mauldin "Books and Men," in The Atlantic, volume 180 (1948):

Several Catholic dignitaries made angry mutters about the picture, and the Brooklyn Tablet, which has stanchly supported Father Coughlin's Christian Front, and which suspects everybody but the toughest conservative of being a communist, ran a front-page editorial about the cartoon, with a headline stating that the New York Herald Tribune (a steady Republican paper) was going pink because it had printed the drawing. Several organs of the Knights of Columbus reprinted the Tablet editorial, and added a few choice words of their own.

It's the first time in my life I have been so roundly cussed in print, and I reacted as do most people who make a career of poking at other people and who suddenly find that they have to put up with a little of what they dish out; I didn't take it so well.

From Proceedings of the Annual Convention of the National Association of Animal Breeders (1970[?]):

I have some choice words for certain temperaments [in milk cows] I do not think lend themselves to top production. Mean, goosey, scary, timid, and stupid are a few of them. I use other words when I speak directly to these cows. The ideal temperament is alert, friendly, and gentle—in other words—a pleasing personality. Cows must be aggressive in their eating habits.

And from West's Southern Reporter (2000):

Suppose instead of speaking among friends, one goes to a theater to watch a movie but finds the movie uninteresting, gets up to leave and while doing so employs some choice words that we all could agree would be vulgar, to describe the movie, but the words are not directed at any particular individual.

Clearly the uplifting sense of the original use of "some [or a few] choice words" has been subverted in a number of later cases by the subsequent euphemistic use. And yet both senses of the phrase continue to appear in print. Under the circumstances, to interpret the sense of the expression in a particular case, you must take into account the context in which it appears.

In the poster's example, the phrase "you’ve learned some choice words for people who do that [namely assume that a hypothetical or generic person whose gender has not previously been specified is male]" probably means "some choice words" in the sense of "some highly critical words." But every situation is different, and here, more context would make an accurate interpretation easier.

(As a matter of fact, you can find the entire original text that the poster asks about at Scott Alexander, "SSC Gives a Graduation Speech"—and from that longer piece it is evident that " – this time I’m assuming you’re a man, I’m sure over the past four years you’ve learned some choice words for people who do that" is an aside to his audience of graduating college seniors, who have been attending college for the previous four years and are presumably attuned to gender-based assumptions and criticisms thereof.)

Update (April 15, 2020): Early relevant newspaper instances of 'a few choice words' and 'some choice words'

The earliest newspaper mention of "a few choice words" that an Elephind newspaper database search finds appears in "New South Wales Alliance for the Suppression of Intemperance. The Monster Soiree at the Prince of Wales," in the [Sydney, New South Wales] Empire (June 26, 1857):

I may at this stage of the proceedings give you what will perhaps be the comfortable intimation, that we are not going to make long speeches to-night. (Cheers and laughter.) You are going to listen to something more delightful than speeches. (Cheers.) I have already said my say, but I must tell you that I shall be succeeded by three reverend gentlemen, who will very ably address you. But they will, I trust—and I cannot doubt they will—display their ability to-night, not so much in the eloquence of their strains, as in the conciseness of their sentences. (Cheers.) You will listen to a few choice words also from our highly esteemed friend—a teetotaler to the back-bone—the Rev. George Mackie (cheers) ; and thirdly and lastly, you will listen to our young and and eloquent friend the Rev. Samuel Kent. (Cheers.) I will now, ladies and gentlemen, call upon the Venerable Archdeacon to address you. (Loud cheers.)

The earliest U.S. newspaper occurrence of "a few choice words" in this earlier sense of the expression appears in "Our Religious Column: Church Choirs," in the [Philadelphia] Evening Telegraph (March 6, 1869):

Bassoon gathers up his strength, and with turgid veins and countenance streaming with perspiration heaves up "O Lord!"The Fuffs take up the strain and renew the domestic contest with despairing valor. The sharp-voiced Seraphina Angelica launches her contribution on the air like so much commercial vinegar, a basis of nitric acid diluted to a palatable degree of safety. Fugaciously they toss the ejaculation back at each other, accompanied with a few choice words, apparently from some part of the Old Testament in the original tongue. Then all the chorus singers join in the general burst of the finality of the "voluntary."

Th modern, ironical twist on "a few choice words appears at least as early as this instance from an untitled item in the Hay [New South Wales] Standard and Advertiser (February 17, 1892):

An amusing account is given of a Highland piper belonging to the British troops who fought at Maida encountering in the streets of an Italian town an Italian piper busy charming the ears of his countrymen with the strains of his primitive instrument. The Highlander stopped with astonishment at the curious pipes from which proceeded the feeble sounds. Then in a little time astonishment gave place to contempt on the face of the Gael. Muttering a few choice words of Gaelic, he suddenly threw the drone of the great Highland bagpipes over his shoulders, blew up the bag, and set free a hurricane of sound, compared with which the Italian trills were indeed tame. The piper marched right upon the agonised Italian, who retreated behind the Highland blast, and at last fairly ran, and left Donald master of the street.

Likewise, for "some choice words" in the modern sense, we have from "Current Topics," in the Burra [South Australia] Record (November 2, 1892):

Smith was in a bit of a pickle as he was not in possession of the amount of the hearing fee ; he asked the S.M. to allow it to stand over until the case was heard. 'We don't give tick' said Mr. Edmunds, but subsequently granted the request and Smith proceeded. Some choice words were exchanged in the excitement, Smith finishing up by saying the baker was a—well a naughty man (to put it mild). The defendant said Smith charged at the rate of 7s 6d per hour for his work, to which the plaintiff replied (and no doubt it was true) 'I can do a lot of work in two hours if I'm on piece but if I'm on day work I can do very little.' This remark brought a laugh from all the working men present, who had no where else to go just then owing to operations being suspended in the quarries.