[TimMason]

A quick aside on kinds of knowledge. Psychologists distinguish between two kinds of knowledge: declarative and performative. This first is made known through language, the second through performance. One of the questions that they wonder about is the relationship between the two. Some thing that, in the end, all human knowledge is declarative, others say that, no, you can learn without spelling out the rules, through guided performance.

What Beppe was arguing for is that Plato or his slave could be taught how to ride a bike through guided performance. However, observations of parents teaching their children how to ride bikes suggest that this may be a simplified vision: in fact, parents do guide the child through modeling and physical interventions - hanging on the back of the saddle, for example. But they also give a lot of verbal advice, telling them how to hold the handle-bars, and how to turn them at the right moment, when to push and with which foot, and so on. They also, of course, give lots of advice about how to ride on roads where there may be other traffic (the Highway Code is declarative).

This kind of consideration has led some of them to conclude that *all* knowledge is, in fact, declarative, only the learner may have forgotten the specific declarations. If this is the case, then the learner should, with perhaps a lot of trouble, be able to restore his or her knowledge to its declarative form - thus enabling the construction of an expert system.

If this is so, Beppe will not be able to simply show Plato or his slave how to ride a bike, but will have to give instructions. Perhaps he had better bring his wife with him to the meeting on the Champs Elysée.