Now, you might think that if "more" can be used with both count and mass nouns, so can "less". But it doesn't work that way: you may have "less gravel", but most writers agree that you can only have "fewer pebbles", not "less pebbles". This is a reasonable distinction, but purists have extended it with a vengeance. The sign over supermarket express checkout lanes, "Ten Items or Less", is a grammatical error, they say, and as a result of their carping upscale supermarkets have replaced the signs with "Ten Items or Fewer". By this logic, off licences should refuse to sell beer to customers who are "fewer than 21 years old" and law-abiding motorists should drive at "fewer than 70 miles an hour". And once you master this distinction, well, that's one fewer thing for you to worry about.No, I think Pinker botches it.
Clearly, the purists have botched the "less-fewer" distinction.
"X less than Y" means X < Y, as real numbers. "X fewer than Y" means X ≤ Y-1, as integers. You do not say "fewer than 70 miles an hour" because that would mean 69 mph or less, whereas a speed limit of 70 mph means that 69.9 mph is allowed.
"Ten Items or Less" makes sense because 9.5 items would be allowed, if the supermarket sold half items.
The term "less pebbles" seems to be used about the same as "fewer pebbles". The word "fewer" might be preferred if you are counting the pebbles, but in most situations, "less" is just as good.
I am saying that the less/fewer distinction is about real numbers and integers, and not about mass and counting nouns.
Pinker also gives his blessing to "very unique", and presumably "more unique". Again, I don't think that he gets to the heart of what is really a math problem, not a linguistic problem.
The word "unique" means unequal to all others. It is not clear how something can be very unequal or more unequal. If you want to emphasize how different something is, you could say that it is very different. X is very different from Y if |X-Y| is large. But something being more different does not make it more unique. 10 is more different from 2 than 3, but it is not more unique.
Great writers have been modifying absolute adjectives for centuries, including the framers of the American Constitution, who sought "a more perfect union". Many of the examples pass unnoticed by careful writers, including "nothing could be more certain" and "there could be no more perfect spot". Though the phrase "very unique" is universally despised, other modifications of "unique" are unobjectionable, as when Martin Luther King wrote, "I am in the rather unique position of being the son, the grandson, and the great grandson of preachers."King was "rather unique", but not claiming to be more unique than others. The trouble with "very unique" is that it claims to be more unequal than others, and that makes no sense.
The term "more perfect" has the obvious math interpretation of being closer to 100% of what it is supposed to be. My dictionary gives these examples:
"a perfect circle"; "a perfect reproduction"; "perfect happiness"; "perfect manners"; "a perfect specimen"; "a perfect day"; "a perfect idiot"; "perfect timing"Most of these uses are such that a perfect example could be replaced by a more perfect example. The one exception might be the perfect circle, if it is an abstract mathematical circle. But then you would not call it "perfect", because all such circles are perfect anyway. In all other cases, the perfect can be more perfect.