fewer and less

My ranga friend was saying that she was forever grateful to the person who taught her to remember that you had fewer peas and less potato.  Fewer peas because these were a number of countable items on your plate, but less potato (mashed) because this was just one undifferentiated blob on your plate.

 This worked well, she said, until she found herself in the supermarket staring at the sign that offered a checkout for those with less than 12 items.  Less than 12 items sounded perfectly ok, and yet by the rule given to her it should be fewer than 12 items.  On the other hand fewer than 12 items sounded artificial and unconvincing.

 Clearly the mantra was no protection against the real world.  There was a danger she was about to go over to the dark side, the world of undifferentiated peas and potato. Red was adamant that she had lost faith completely in the one piece of grammatical wisdom she thought she could trust.

 But what she didn’t realise is that there is a sub-rule.  If there is an element of comparison involved then you use greater than and pair it with less than.  In this instance the people with greater than 12 items in their trolleys went one way, while those with less than 12 items went the other way.

 Will she be pleased when I tell her this? Will it make it better or worse that the simple mantra now has the complication of a sub-rule to negotiate? I fear a grammatical explosion.