Is learning theory really answering the right questions?

More precisely, does working on (statistical) learning theory bounds really help designing better algorithms?

Let me first say that this note is not against anyone in particular.

I know most of the people working on SLT bounds and I do have a lot of respect for them, and I also wrote papers that were trying to justify an algorithm from a theoretical analysis. So I am just questioning the approach but not judging anyone following it!

I have spent a lot of time thinking about what theory did really bring that could not have been obtained without it. Because this is really the question. If you consider the algorithms that people use in practice, the two important questions are whether any of those algorithms could not have been inspired by considerations of a non-SLT nature, and whether the SLT analysis brings an understanding of why they work.

Regarding the first one (inspiration), it is risky to tell what could have inspired an algorithm a posteriori. But I believe that the amount of effort spent on trying to prove bounds and then obtain a criterion to minimize for an algorithm would be better used if people were just trying to find new criteria directly. Indeed, there are surely many ideas that we (theoreticians) refrain from trying or even expressing, because we do not see how they are connected to the standard patterns of SLT analysis!

Regarding the second one (whether bounds justify an algorithm), I would be even less confident: the only thing we can infer from most learning theory bounds is that the algorithm we are studying is not meaningless, that is, it will eventually make good predictions (with enough samples), but these bounds cannot really help comparing two algorithms. Also, they rarely (if ever) can justify the use of a specific criterion.

So, I think that the theoretical analysis is mainly a way to popularize an algorithm and to raise its visibility. The effect is then that more people try it out, and streamline it. So in the end, the algorithm may be adopted, but a theoretical analysis rarely justifies the algorithm and never provides guarantees. Hence theory is a way to attract attention to an algorithm.

It should also be a way to get new insights for the development of new algorithms, but this happens much less frequently than is claimed!

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