In the Orthodox Church, sin isn't necessarily something that we will to happen. It's something that's part and parcel of being a broken human. Indeed, one of our most oft-repeated prayers asks God for forgiveness of sins "voluntary or involuntary, committed in knowledge or in ingnorance".
Wow, Schultz -- thanks. Your statement unlocks a lot of questions I've had about sin and penance in Orthodoxy.
It seems to me that nocturnal emission is not "sin of omission". If, say, someone is being discriminated against and an observer does not speak up about the injustice, the observer could have committed a sin of omission. Psychosomatism isn't omission, since there's no reflection (unless one thinks that dream thoughts are consciously reflexive.) I don't, so I would say that psychosomatic acts outside of the "natural order" are neither sins of commission or omission.
So Orthodoxy has a third "fallen-ness" that's outside of commission or omission? This reminds me of certain commandments of observant Judaism, specifically niddah
(commandments that concern the interaction of menstruating women with other people). Today we know empirically that menstruation is not pathological. Still, observant Jews observe the rabbinical social protocols that concern menstruation even if the rabbinical commentary or the Mosaic prohibition contradict current empirical knowledge.
Is the Orthodox evaluation of involuntary emission of semen akin to niddah? Is the production of a life-generating substance outside of life-generation the occasion for penance? Or, is this a matter of ritual purity? Fascinating topic.