Question: I have trouble with this sentence. "Reason" is singular and I want to use the present tense, not the past. 

Which one is the correct one? 

> 
> * The reason **lays** in the facts
> * The reason **lies** in the facts
> 
> 
> 

Thanks a lot

Context: this sentence is used as an argument encouraging the other persons to look at the facts as they will provide the reason.

Answer: 
You asked for the *present tense,* and it's easy! 

The correct one is...

> 
> The reason *lies* in the facts.
> 
> 
> 

Quick tip is -**broadly,** the word *lay* requires a direct object and *lie* does not. That said, you can *lie down* on the floor but you *lay your laptop* on the table. 

---

The things go haywire when it comes to the past tense. Because the past tense of *lie* is *lay!*.

Good read is here on [GrammarGirl](http://www.quickanddirtytips.com/education/grammar/lay-versus-lie?page=1).
If `The reason lays in the facts` would have continued on, the usage of 'lays' could have been right too. For example:

> 
> The reason *(for his action)* lays in the facts not told.
> 
> 
> 

Other example could be "The Internet lays foundation for a new generation of communication vectors."