I think that much can be learned from observations about the external world. Outwardly appearance is a form of physical expression, right? I call it the Ego(others have different definitions of the term, but as for now, this is mine)

From the ego(as well as all physical manifestations) you can follow observations along with logical steps to arrive at conclusions.
I'll give an example of what I mean.

You're wearing a shirt from a band. This could lead us to several conclusions. One, you like the band. Two you've seen the band live and could have bought a the t-shirt at the show. etc. etc.

I guess the point i'm trying to make is don't just disregard the physical attributes people choose to present when trying to determine, this, that or what ever from them.

I'll give you another example, you said,"don't judge a book by its cover" but you are saying this because someone told you this, right?

Yet, as far as I am concerned anyway, you only see the proverbial book cover of a person(Their ego ). The only pages of a book you see is the current one you are reading fully(your personal consciousness) . In other words, you are only experiencing the inner workings of your own mind, so you can not, EVER, see the inner workings of somebody elses mind, because you are contained inside your self as a singular actor.

I do agree with one of you main points, thinking things through.