the paradox of the grandma present

[raaaid]

1st my apologies for the other thread, farthest from my intention to be ofensive, as a matter of fact i tried to soften the original story

ill make a kids aproach now:

granma told told tommy that as he had been a good kid she would buy a present for him

she told him she would give the present to him a class day at supper time and that it WOULD CAUGHT HIM BY SURPRISE

tommy started to wonder when granma woud give him the present:

he concluded that if thursday supper passed by and grandma didnt give him the present he would know for sure it would be on friday, SO THERE WOULD BE NO SURPRISE

so friday was ruled out as the gift day

so the present could arrive on monday or tuesday or wednesday or thursday if it was to be a surpirse

but then he could use the same reasoning if wedenesday supper passed by he would know the day his grandma chose to give him the present would be thursday

and tommy went on and on and conclude grandma had lied for it could not be a surprise

yet tuesday arrive and tommy got a very nice present and indeed was surprised

so whats wrong here?

btw thanks for the lesson alpha