I'm responding to the creator's original post.
While it is true that language affects the way the human mind thinks, it is certainly possible to use your brain to full capacity, even if you were unable to communicate in any way.
It goes kind of like this-
When you are born, you have a Tabula Rasa. A clean slate. An empty mind. When you see your first cat, you do not know that it is called a "cat". You do not really know anything about it; whether it is the only one of its kind, whether it is a different cat from the next on you see, etc. But as you progress, you pile more and more objects into your "clean slate" so that now when you look at something that is big, red, and spherical, you think of a big red ball. You are able to reference these things by comparing them to other objects or experiences you have encountered, or read about, or whatever.
So language is simply a method of speaking aloud (or signing, or writing, communicating) these "forms" your slate has absorbed and filed away.
Think about it - what are all mythological creatures like? Other, real creatures.
A pegasus is just a horse with wings.
A dragon is a winged, or unwinged magical serpent.
A griffin is a mix between an eagle and a lion.
A chimera is a grotesque combination of monkey, goat, serpent, lion, and rooster (or any combination of animals, depending on the origin).
The human brain cannot postulate things it has no comparison for. It is impossible to think of an idea, or mythological animal, or alien, or sense, or emotion, or color that is not a derivative or synthesis of "forms" you have experienced in your life time.
But to actually answer your question - yes, a person without any idea of a codified "language" would still possess the cumulative experiences it has witnessed, and be able to contemplate them entirely internally.