Like I said, theres a certain period where there isnt enough of a developed body for a soul to reside there (kind of like there isnt enough room) and then beyond that point the soul enters the body. This is usually past first term. The date of course varies, but its never inactive by about mid-third term. Remember, the body cannot survive extended periods of time without a soul, and the baby usually becomes much more active around the second term. This isnt just because of muscle development. You can feel the energy of the baby changing to that of a (well, semi) conscious life form. (Also whoever is arguing that theres no way to know, thats my proof. If you pay attention, you can tell)