User blog comment:Godisme/My Take on Isshin/@comment-1743015-20100328050253

You're right. See: Ichigo was made a Vizard through natural means (Encroachment) and the other Vizard were made so through artificial means (Aizen's unnamed virus. Tosen was the same, he got his powers from the Hogyoku, making him an artificially-created hollow-hybrid. That theory may be accurate, but here's something else. In chapter 396, Aizen was explaining Ichigo's develop, from him gaining his Shinigami powers to defeating Ulquiorra becoming even stronger. If Aizen really is after his Hollow, why'd he include Ichigo's hollow powers in his development list of Ichigo? if he was after his Hollow powers, then he would've left them off his list. Besides, remember: Aizen has the Hogyoku. Even though he stated he would never bother hollowfying, he could still obtain a hollowification from the Hogyoku.