I figured he was a lot like many grammar column readers — the kind of person who would have made note of the correct use of “lay” and “lie” at some point or other. If his memory on the matter had gotten fuzzy, surely it was time to revisit it.
But he was not fuzzy on the subject. He nailed it. I was on my way back to the column-idea drawing board when it hit me to ask a follow-up question: “What about in the past? Yesterday, did you lay down or lie down?”
“Oh, the past is different,” he said.
“How so?” I asked.
“In the past, the rule doesn’t apply,” he said.
That’s as far as he got, giving me all the reason I needed to fulfill Roger’s request: The difference between “lay” and “lie” is simple — until it’s not.
The basic difference is that “lay” requires an object and “lie” does not.
You can’t just lay. You must lay something. In “David lays the book on the table,” the object of the verb is “the book.” David’s acting upon something else. This is called a transitive verb.
Conversely, “to lie” is intransitive. In “David lies down” and “David lies on the couch,” David’s not acting upon some object. He’s just lying down.
It would be were it not for one cruel little twist: The past tense of “lie” just happens to be “lay.” So today, David lies on the couch. But yesterday he lay on the couch.
Where does “laid” come in, you ask? Well, that’s the past tense of “lay.” Today Donna lays the book on the table. Yesterday she laid the book on the table.