Board Thread:Questions and Answers/@comment-27015288-20160119152648/@comment-44061-20160121133443

Well yea i think thats the rub. It does say in battle its not uncommon for one to switch entirely to using reiatsu sense on a subconscious level as there only way of gaining information. There are two possibilities as far as i see it.

1.) The problem presented here is when Yamamoto caught Aizen in his trap. He specifically points out that he knows Aizen is the real thing and not an illusion cause he can sense the reiatsu from his zanpakuto. Your right that the Illusions created by Aizen affect the 5 senses and not the reiatsu sense. My best guess would be reiatsu sense requires conscious use and even if for higher lvl combatants use it subconsciously i would be under the impression that like most things in this universe it requires practice and experience to use it subconsciously or in any affective way. Thats the only possible concept i can come up with for why everyone falls for it.

2.) There is a possibility that Aizen keeps his reiatsu hidden/close to his person, that would make the most sense given the nature of his ability is subterfuge and espionage. That would also account for the fact that he can move around undetected during the SS arc.