Comment Re:Ordering and Convergence (Score 1) 981
The fact that the number of days in a week is arbitrary is completely irrelevant. If there were eight days a week, then could make the same calculations, substituting the number eight for seven in the calculations. Yes, the results would be different but that's because the information you were provided is different. In this case, the day the son was born is narrowed to one in seven. If there were eight days a week, it would be narrowed to one in eight.
The number of sides on a die is arbitrary as well. There are dice with 4 sides, 8 sides, 10 sides, 20 sides, etc. On a six sided die, the chance of rolling a one is one in six. On a ten sides die, it's one in ten. Just because a six sided die is an arbitrary choice doesn't mean that one can't calculate odds based on that number. So long as you know the size of the die being used, the odds are directly calculable. So long as everyone understand the number of days in a week, the odds can be calculated based on that as well.