If an AI understands is a topic of debate. Seldom debated, however, are the limits of our own understanding. We imagine our understanding as complete and establish this as a baseline for AI. A different framing appears when we concede our understanding as incomplete and apply this to AI.

The fundamental issue goes like this:

An AI may describe an apple as "sweet" though it has never tasted one, "red" though it has never seen one, and "smooth" though it has never felt one. So while an AI may skillfully apply the word “apple”, in what way, if any, can we say an AI understands the word “apple”?

Steven Sarnad named this the “symbol grounding problem." He reasoned that the symbols we use as reference must be grounded, or referent, in phenomena to be meaningful. After all, the word “apple” when written in a book has no meaning on its own. Meaning of symbols is “parasitic on the meanings in our heads” he writes.^[1] To Sarnad, the AI doesn’t understand at all, only we do, as only we can bridge the gap between reference and referent.

Yet now we have AIs that seem to ground text in images.^[2] Have we proved Sarnad wrong? Do these AIs understand something previous AIs did not? Predating Sarnad, John Searle, with keen foresight, addressed this issue. In Minds, Brains and Programs, Searle fashions and then refutes the “Robot Reply” argument. He describes an AI that would “have a television camera attached to it that enabled it to 'see,' it would have arms and legs that enabled it to 'act,' and all of this would be controlled by its computer 'brain’.”^[3] Yet to Searle, this “adds nothing” to the argument. We are simply introducing more symbols, and to exploit correlations in symbols between modalities is no different than exploiting correlations within a modality. To Searle, grounding was neither the problem, nor the solution, to semantics arising from syntax.

So just what is a grounded AI lacking? On this question, Sarnad and Searle are silent. Less silent, though, were the empiricists predating them. We attempt to get at our question by asking what they asked: what are grounded human minds lacking?

Back to the apple. The empiricists accept that the sweetness, redness and smoothness of an apple is a manifestation of our minds. Outside the mind, apples have no taste, color or texture. These properties make up the phenomena of apples. To know what an “apple” is ou...

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