Validate a "Two part name"???

Validate a "Two part name"???

Hi!!!
My question is how can I validate a field where user introduces his name???
The thing is that if the user´s name is just "Mario" I use this to validate:

<

script type = "text/javascript" >

jQuery.validator.addMethod(

"lettersonly" , function (value, element) {

return this .optional(element) || /^[a-z]+$/i.test(value);

},

"Only letters...!!!" );

</

script >

An this is enough to validate that, but what if user´s name is "Mario Luiggi"

If anybody knows how to validate a "two part name" please let me know...

PD: Just in case, the code I wrote it´s not helpful because if I write "Mario Luiggi" I think Jquery takes the space between the two names as a number and of course I don´t want the user to be allowed to enter numbers too (¬¬)