Symbol grounding

I agree with Werbos' definition of intelligence, "a system to handle all of the calculations from crude inputs through to overt actions in an adaptive way so as to maximize some measure of performance over time" (IEEE Trans. Systems, Mind , and Cybernetics, 1987, pg 7).  A brain is a control system.  In any artificial intelligence all symbols (internal representations) are then surely grounded in so far as they functionally connect sensory and utility/value inputs with outputs/responses. But in deep (complex) networks some symbols will be far removed from primitive/raw perceptions. i.e., more "abstract" concepts.