RL systems do experiment by that definition. For instance, DeepMind's first Atari player used an epsilon-greedy exploration/exploitation strategy: choose the ac

RL systems do experiment by that definition. For instance, DeepMind's first Atari player used an epsilon-greedy exploration/exploitation strategy: choose the action the model suggests is best with probability 1 - e, choose a random action (that is, "try different things") with probability e. I don't what you mean by the "system's output" when talking about theories, but it seems to me that even by your definition, the weights of the ANN can be understood as a theory. Having several theories is the same as having one theory, "one of these theories is more correct", or possibly "some combination of these theories is correct". If you define it as one theory instead of several, you can still improve it. (As I recall, some RL systems have multiple "heads", in a way corresponding to multiple theories).