Instituut voor Taal- en Kennistechnologie
Institute for Language Technology and Artificial Intelligence

Harnad responds

Fetzer thinks TTT grounding is based on an isomorphism between internal symbols and features of the world. It is not. You could have isomorphism with the world (under an interpretation) in an ungrounded symbol system. The TTT requires full causal interaction with the real world of objects and their features, and the capacity for this must be indistinguishable from our own. This is not an ``experiential'' test but an empirical one: The robotic capacities (to discriminate, categorize, identify, manipulate, describe, and discourse about objects) must really be there, and really exercised, and really not discriminably different from those of a real human being.

This is not behaviorism, it is reverse engineering: Fetzer asks for a theory; the theory will be the full description of the internal structures and processes that succeeded in making the robot pass the TTT. I don't know what Fetzer's ``motives, beliefs, ethics, etc.'' are, but once we know exactly what internal (robotic) states actually deliver the TTT goods, we may be able to fill in the blanks with those. What does not look as if it will do is an internal something that is ``aware'' of signs or symbols, for then the job begins with finding out what internal structures and processes that homuncular module consists of. The only internal causes and effects I can imagine adding to this engineering assignment would amount to moving toward the TTTT [see Response to Bringsjord] (which I would consider helpful only inasmuch as it gave hints to accelerate our progress toward passing the TTT).