Board Thread:Theories and Speculation/@comment-30323490-20170305205254/@comment-9782468-20170307163549

LegionZero wrote: Everyone has the opportunity to learn Sage Mode. Minato and Jiraiya, who don't have anything in particular special about them besides their own natural high chakra levels, learned it.

High chakra levels fall within the "no outside source" category. Techniques like Raikiri require high amounts of chakra.

The ability to sense, gather, and harness Natrual Energy can be achieved naturally, with ones own skill and hard work. Unlike EMS, Rinnegan, Tenseigan, RinneSharingan, or through implants. Therefore, valid. You said that Jiraiya and Minato learned Sage Mode despite not having anything special about them, then quoted the exact thing that set them apart that allowed them to use Sage Mode in the first place.

If Madara summons Kurama and forcibly takes chakra from him, do we not consider it an outside source? Before the Jinjuuriki, the Tailed Beasts were just huge masses of chakra that could be controlled by anyone who trained enough. Is it not an outside source?

Meh, neither you nor @Vlad have convinced me, but I doubt I can convince either of you so I'll just agree to disagree on this one. And since I disagree with the OP on a subjective portion of the requirements, I'll duck out of the discussion. I'll still read though, it's an interesting topic.