Let me ask you then.
What do you know?
Are you able to know anything you don't personally do?
I've never sky jumped before but i KNOW that if I don't open my chute i'm fuked.
I've never shoved a fork in an electric socket but based on what I know of electricity because of reading i KNOW i'm gonna get shocked. (I guess I must know some type of...magic...then right? I mean how can i know if I've never done it.)
How about gravity? Have you ever calculated earths gravity? I mean actually done the experimentation to arrive at the pull on objects? I know people who have NEVER done this, and yet...they know gravity is there. OMGWTF!!! HOW?
Clearly you cannot learn everything from a book, but yes if someone went down to the ocean floor and discovered it was made of pudding, they too samples over 1/3 of the ocean floor and confirmed that YUP it's pudding, does that mean I could never say i know the ocean floor is made of pudding?
Actually the ironic part is that per your line of ...thought...
I'm equally as accurate saying the ocean floor is made of pudding as I am saying it's made of dirt.
And you clearly see no problem with this?
Stop posting right now, right this instant and go to a library, ask for the science section and read, read until you can't read no more.