(Similarly, selfishness is either egoistic or not selfish.)
I found this out by thinking about the mechanics of an epiphenomenal consciousness. The problem is that our consciousnesses in particular think that they are in control of material objects; to whit, my cellular body. Epiphenomenalism is the hypothesis that this isn't true.
However, how does the epiphenomenal mind know which things to think it is in control of? The only way is if the physical causes it to know; one-way causation. You think of picking up a phone, your cells indeed pick up a phone, which means the physical brain, which decided to pick up the phone, informed your epiphenomenal mind that it was going to do so. Otherwise, you'd immediately notice the fact of epiphenomenalism, because you'd decide to pick up the phone, but you wouldn't actually do it. The mind has no effect on the physics, but the physics happily chains the mind.
This means the mind just is the physics. The mind does whatever the physics tells it to do, and nothing else. The mind is simply another aspect of the physics.
Which means that epiphenomalism cannot be true, as it is self-contradictory. (Just as selfishness cannot be the opposite of altruism, as that would be contradictory.)
Epiphenomenalism is proposing something which is part of the physics but doesn't do anything. If you remove the epiphenomenal mind from your model, the model's predictions do not change, which means if you removed the epiphenomenal mind from a world, the world would not change.
It is trying to tack something onto the physics, but it doesn't work. Its descriptions of the proposed thing all boil down to mean nothing.
For me, this is a longer and parochial proof that existence means interaction. If you can poke it, it can poke you back. If you can't poke it, it cannot exist in any meaningful sense.
Of course you're welcome to be wrong, but if you think epiphenomenalism is coherent, that altruism isn't selfish, or that things can exist yet be immune to experiment, you're simply wrong.
"James (1879), who rejected the view, characterized epiphenomenalists' mental events as not affecting the brain activity that produces them “any more than a shadow reacts upon the steps of the traveller whom it accompanies”."Shadows affect the traveller. Specifically, it has an effect like a slight pressure. Light has energy, which means mass. By blocking the light, the traveller will feel a small gravitational pull everywhere except from the shadow, which amounts to a slight pressure. More transparent travellers will feel less pressure.
While this pressure is probably below the noise threshold, it is inevitably associated with other events which are not, such as the appearance of the shadow. I claim that James did not simply err in his choice of example, there are no such examples anywhere.