Which is another huge essay to read and does not adequately answer the objection. There are for example four fundamental forces. Are we going to find another four? Maybe we can find a fifth, but that is pushing the frontier. if such a force exists, its obviously going to be much harder to find than the others. Same for fundamental particles. There are 16 of them, plus Higgs. Are we going to find another 17? Or 3 battery types. I think psychology is different because you can always find new permutations of experiments.