People with an INFJ Type Pattern are very much able to connect ideas and understand concepts quickly with a focus on the human condition as a whole; they use what they know and integrate their knowledge through connecting with people. This allows them to understand whatever worldview, system or concept they strive for.
People on here who say INFJs can "read people's souls" are just drinking the Kool-Aid.
Be realistic and describe it properly as opposed to making it out to be something overly fantastical.
As for weaknesses, some INFJs, depending on their level of development, may be so engrossed in understanding how their worldview could make a difference in the world, that they forget what is happening right now.
They will miss the sounds of nature, how food tastes; they want to finish things quickly so they can continue to think deeply about whatever it is they enjoy thinking about [without distraction]. The best thing for an INFJ to do is immerse him/herself in the present moment, and try not to think deeply [all the time] about meaning.
This will, in essence, balance out the individual using the INFJ Type Pattern.