Is that just a thought experiment? Almost all mental illnesses I am aware of seem to be experienced continuously, maybe with an ebb and flow in intensity. But

Is that just a thought experiment? Almost all mental illnesses I am aware of seem to be experienced continuously, maybe with an ebb and flow in intensity. But even if such a person existed and the phobia wasn't persistent without a doubt the person would suffer from related anxieties. I don't believe that you could suffer from such a condition and be mentally well for any amount of time, although I certainly see your point that during certain periods the person might be able to make an informed decision.