Suppose it is Wednesday:
Does the expression "This Monday" mean:
- The Monday of the same week.
- The Monday of the following week.
Does the expression "Next Monday" mean:
- The Monday of the following week.
- The Monday of the week following the following week.
As an aside, I'm not even sure if the fact that this would work one way rather than another is a matter of which language is spoken (e.g. English), or whether the same reasoning as would be given by answers on this group would apply to other languages as well (as a matter of pure logic).