It's the same with neurology. We pretend we understand how the brain works, but much of what we are understanding is our current conceptual knowledge, so it's theoretical.
We work with Phase-targeted auditory stimulation to enhance deep sleep (https://affectablesleep.com). We know we can stimulate the brain during sleep and measure the increase in electrical activity which is the result of increased synchronous firing of neurons, but the reason why we are able to create this result is just a theory. However, the behaviour itself is consistent, and replicated.
We work with Phase-targeted auditory stimulation to enhance deep sleep (https://affectablesleep.com). We know we can stimulate the brain during sleep and measure the increase in electrical activity which is the result of increased synchronous firing of neurons, but the reason why we are able to create this result is just a theory. However, the behaviour itself is consistent, and replicated.