I wrestle with this question every year.  I know that my son is intelligent and rational.  I know that the belief in Santa is completely the product of us nudging him in that direction.  He is smart enough to question, but we provide the right incentives for him to continue the belief.  I was not fully sure until around his age, and the news was heartbreaking.

I struggle with this question because I know that the belief in Santa is no different than the beliefs he will be taught in school (particularly high school civics).  The belief in government (politicians are hyper-moral and hyper-rational beings, above society in some vague and indescribable way).  I raise my son not to believe in such nonsense.  I tell him the truth about government (just people with power who have convinced others that their power is legitimate and that all of this is somehow consensual because it was written on a piece of paper by people who are dead now).  

Should I tell him the truth about Santa?