Joan Wickersham op-ed in Globe last Saturday, on grammar:
But before you go lie down, you’ll need to lay down your fork. “To lie,” means “to recline”; “to lay” means “to place or put.”
That’s pretty straightforward, assuming that this is all happening right now. But suppose it happened yesterday? Suppose that yesterday you ate a lot, and then you got rid of your fork and then reclined? It would be correct to write, “Yesterday I laid down my fork and then I lay down.”
So can we say that if you recline today it’s “lie,” and if you reclined yesterday it’s “lay”? Not exactly. Suppose you want to say that yesterday at your grandmother’s you ate a lot and then made a decision to go and recline? It happened in the past, and yet the correct way to say it is, “I decided to lie down.”
Because “lay” is the simple past tense of the verb “lie,” but in the sentence “I decided to lie down,” “to lie” is the infinitive form of the verb, which here functions as the object of the simple-past-tense verb “decided.” That’s why.
She’s right, of course.
On the other hand, I cannot actually bring myself to use the past tense of “to lie down,” in any situation where I feel required to use it correctly. In a blog post, I’ll instead write something like “decide to lie down,” rather than write “lay down,” which seems stilted and actually a little bizarre. In an IM I will probably write “laid,” though occasionally I get self-conscious about this and write “lay.”
I’m always pleased when I'm reading a children’s book to my daughter and it uses the word “lay” correctly, especially when it’s also used elegantly. That doesn’t happen very often. (Most American picture books, in particular, seem wedded to the idea of the casual.)
What does get on my nerves is the use of “as” for “while.” This doesn’t seem grammatical in the slightest; and maybe it’s colloquial somewhere, but I’ve never heard it in speech, any more than I’ve seen it in print. I suppose it’s easier for a child to read than “while” is, and it’s probably more likely to be on basic word lists. But what it feels is like a reactive attempt to avoid either “like” (which doesn’t actually fit anyway), or the whole controversy over the proper use of words like “since” (which doesn’t fit either but at least is close).