A fellow Dharma practitioner friend of mine and I (who both intend on becoming monks) were discussing a basic difference in two types of practitioners:
There are those who conform the Dharma to their perspective, and those who conform their perspective to the Dharma. By the first type of person, I mean someone who wishes not to change their conduct, so they interpret the teachings a certain way (naturally, this isn't an intentional distortion), and then proceed to take teacher's words out of context to support such claims. On the latter end, there are those who understand the Dharma and see that their perceptions and behaviors do not align with it, so they change themselves in order to fit the teachings. I am not stating if anyone here is either.
Also, a good point was made about the health benefits of masturbation. It is medically encouraged to masturbate daily for a man, as it drastically lowers his chance to develop prostate cancer and other prostate problems. Therein we find a sort of conflicting... How to put it.
Masturbation is indeed healthy. So, even if one did take a vow, it may benefit them to masturbate. However, the thoughts associated with the action largely create attachment and the indulgence of sensual pleasure would not be beneficial to one's practice. So then we have this issue where, if we are concerned about our health, we should masturbate, but in accordance with virtuous lifestyle, do such without thinking of anything and having no attachment to the physical sensation. This act would likely be considered impossible for many people without higher attainments.
So then, the question arises whether one should do something for health reasons and suffer from the karmic backlash, or to go without and be virtuous, but leave oneself open to developing cancer? Well, it is stated many times over that one should put their vow before all else, including their own life. I have a book in which it says if you have taken the "no kill" vow and you had an option between being killed or killing, you should let yourself be killed. On the other hand, I've heard teachers say something different on a similar topic. It was one of the teachers I've been watching a lot recently but I cannot remember which one (recently has been Tsem Tulku Rinpoche, Khandrol Rinpoche, and Dzongsar Khyentse Rinpoche) who said you should never denounce Buddhism, but if someone points a gun at you and demands you denounce all religion, you should say so to the person but not in your heart. So, it seems there is some conflict between these two things among teachers.
Also, I heard a mahayana teaching, it may have been zen, in which a young monk is sent to journey across the sea to another monastery, but falls asleep on the beach. When he wakes up and boards the boat, there is a beautiful woman who is a princess, and over the course of the ride, they fall in love. When they exit, she pleads that he breaks being a monk and elope with her, and he does. They live out a life together, him becoming a prince, and having two children. However, on a boat ride his two children die and he feels overcome with pain. Then, he wakes up, back on the beach, still as a monk. He goes straight to the monastery he was supposed to and tells (I think) the abbot the story of his dream, and the listener replied "That's why I have been masturbating for the past 60 years!" (or something along those lines)
I think this situation is ultimately one of those "if you can go without, then go without. If you can't, then don't." situations where the area on the whole is gray. I do believe in Vajrayana it is not considered proper, but... we are talking about lay vows. Lay practitioners will take a vow not to kill but still eat meat, take a vow to no intoxicants and will still smoke cigarettes or drink coffee, so... letting something slide as far as masturbation is fine.
Also, it has been shown that if someone entertains thoughts of sexual violence (like rape) but then masturbates to porn, that most of the time it winds up being therapeutic and lessens the desire to commit such acts. So perhaps there is some good in the act overall, even aside from the health benefit.
Also, just to clarify, I partake in such an act. Yes, I do plan on becoming a monk, and yes, I plan on taking the celibacy vow very soon. Masturbation is likely going to be the hardest thing for me to give up moreso than any of the other things I have begun giving up.
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OM TARE TUTTARE TURE SOHA
"The world is dark when you're depressed; your thoughts have the power to invent your world." -Courage Wolf
"It is more important to be kind than to be right."
(I acknowledge I do not follow the quote above this, that is why it is there! so I will be reminded every time I post!