Veganism is perhaps the most important issue of all to be thinking about and promoting at this point in time if we are determined on reducing suffering in the world – as we indeed should be. For our exploitation of non-human beings for frivolous purposes, which includes tens of billions of lives lived out under the horrible conditions of factory farming, is no doubt the greatest source of suffering in the world that we can easily abolish (and it is worth noting that a vegan diet, contrary to common objections, in fact is the diet that prevents the most suffering and death). And all it takes to end this suffering is that we, civilized and moral citizens, collectively decide to put an end to it, which makes it unlike, say, the unthinkable torture presently going on in North Korea, which unfortunately seems hard to stop for the ordinary, decent citizen. Furthermore, what it takes and what is being asked of us in order to create a vegan world is really a bare moral minimum, as we are not asked to actively save any non-human animals — no money need be donated, no new inventions need be made. All that is required is that we stop actively supporting the harming and killing of our fellow sentient beings. No heroic or self-sacrificial acts are required.
Another reason why veganism is of great importance that should not be overlooked is that our not being vegan also increases the risk of an existential catastrophe, a catastrophe that causes human life to go extinct, since our raising billions of non-human animals under closely confined conditions inevitably increases the risk of pandemics that could spread sickness and death faster than we can manage to devise a cure.
Lethal pandemics aside, our not being vegan causes many different diseases to spread to human beings, and it also pollutes our environment in ways that make us sick and can be lethal; all in all, our raising of non-human animals causes enormous amounts of human suffering and death — thousands, if not millions, of human deaths every year — in many different ways (I will not elaborate on the ways in which our not being vegan causes human suffering in this essay, as I have done that elsewhere. See the first and especially the second chapter of 'Why We Should Go Vegan').
Yet another reason why veganism is important is that it is the first step toward recognizing the moral value of non-human animals, and toward transcending our speciesism — our discrimination against other beings based on their species membership, which is not in itself an ethically relevant characteristic (In relation to speciesism and its pervasiveness in society, I recommend watching Speciesism: The Movie. See also my book Speciesism: Why It Is Wrong, And The Implications of Rejecting It.)
Our notion that the pain and suffering of non-human beings cannot in any way be compared to human pain and suffering is a speciesist one; as speciesist as it is racist to say that people of color do not experience pain in a way that can be compared to the pain of white people, since it is not in any way supported by a closer study of the neural correlates of pain or suffering, as non-human vertebrates show every sign of having these basic neural structures in common with us. Here is David Pearce pointing out the anything but human substrates of suffering:
We often find it convenient to act as though the capacity to suffer were somehow inseparably bound up with linguistic ability or ratiocinative prowess. Yet there is absolutely no evidence that this is the case, and a great deal that it isn't. The functional regions of the brain which subserve physical agony, the "pain centres", and the mainly limbic substrates of emotion, appear in phylogenetic terms to be remarkably constant in the vertebrate line. The neural pathways involving serotonin, the periaquaductal grey matter, bradykinin, dynorphin, ATP receptors, the major opioid families, substance P etc all existed long before hominids walked the earth. Not merely is the biochemistry of suffering disturbingly similar where not effectively type-identical across a wide spectrum of vertebrate (and even some invertebrate) species. It is at least possible that members of any species whose members have more pain cells exhibiting greater synaptic density than humans sometimes suffer more atrociously than we do, whatever their notional "intelligence".
[Quoted from Pearce's 'The Hedonistic Imperative'.]
This should detonate a bomb in our thinking about ethics and unleash a Copernican Revolution in ethics that finally makes us realize that all moral concerns and obligations do not revolve around us humans alone. It should make us realize that people who fight against racism but not speciesism have taken up an arbitrarily narrow fight against discrimination — speciesism is, after all, very similar to racism, as it is also discrimination based simply on different external traits; the only difference is that racism is discrimination against our close cousins while speciesism is discrimination against our more distantly related sentient cousins.
The fact that we are likely equal with our fellow vertebrates in our capacity to suffer should also make us realize that we are committing an atrocity every day when we raise non-human animals under horrible conditions and kill them, and it should obviously also make us go vegan. We would for instance never accept a practice that forcefully makes women pregnant every year, and then takes away their children right after birth — the boys being killed soon thereafter and the girls being bound to have the same fate as their mothers — in order for us to get milk from these women, no matter how much we enjoy drinking milk or are unable to "give up cheese." Nobody would consider supporting this industry a matter of personal choice — in fact, nobody would consider supporting any exploitation of humans for frivolous purposes a matter of personal choice, no matter what minds or traits the humans who are exploited have, which just reveals that the only reason we consider not being vegan a matter of personal choice is speciesism.
In the case of the imagined human dairy industry, nothing would change in our attitudes if we said that we only exploit women who have a mental disability and who do not understand what is going on; the mere pain and nausea of being pregnant and the pain of labour, along with the sheer lack of necessity, makes it obvious that we should not do this. Yet this is exactly what the dairy industry that most of us happily throw our money after does to innocent cows whom we have every reason to believe suffer as horrible suffering from pregnancy and labour, not to mention the violent insemination they are subjected to, as a human would. This clearly reveals that we have a double-standard, and its source is pure speciesism. If the cows in our dairy industry had had human bodies — say we transplanted the cows' nervous system so that they had the exact same nervous system, and the exact same experiences that they presently have during their most unfortunate lives as dairy cows, but the outward appearance of human beings — people would no doubt be outraged about this practice of forced pregnancy of human-looking beings, and they would no doubt demand that those responsible for it should get the highest punishment possible.
This inconsistency clearly reveals that we need to expand our circle of compassion and ethical consideration so that we need not perform such transplants in order to care for our fellow sentient beings — so that we can stop discriminating against beings based on their outward appearances.
When it comes to human beings who have certain disabilities that make them unable to communicate what they are feeling, we rightly realize a responsibility to help and support, while in the case of non-human animals who are equally unable to speak up for themselves and report how they are feeling (even though their behavior quite clearly gives us good hints about this if we only pay attention), we somehow manage to convince ourselves that we can subjugate and use them as we please. Our speciesism and moral delusion could not be clearer. We would never be tempted to subjugate and kill a human being if we are told that s/he has the exact mental abilities of a cow or a chicken. So why would we subjugate and kill a cow or a chicken for the reason that they have the mental abilities of a cow or a chicken?
All this should make the immense importance of veganism clear: We live in a society where supporting industries that make non-human animals suffer in the most horrible ways is commonplace, and where going against it is considered extreme and something one should keep to oneself. And as long as we partake in it, that is, as long as we are not going vegan, we will fail to see anything truly wrong with it, and the above-mentioned transplant and the human form will continue to be necessary in order to ignite people's ethical concern.
Our descendants will not look upon our practice of subjugating and killing non-human animals as we do, and they will not look at us in the way we do ourselves. They will surely see our time as one where the banality of evil was more evident than ever: the Internet was there, they had the information, they could even see the footage. Yet they shrugged their shoulders and merrily took another bite. Our descendants will no doubt be far more advanced than this. Rather than harming our non-human cousins, our descendants will recognize their ethical obligation to not only not harm non-human beings, but to help them wherever they are, and this is yet another reason why veganism is important: it is the first step toward helping relieve the suffering of non-human beings in nature.
We will not climb toward this ethical high ground before we stop exploiting and abusing non-human animals for frivolous purposes such as palate pleasure, fashion preferences and entertainment, because until we do, we will be inclined to defend a habit rather than do what is ethically right. It all comes back to our custom and habit-bound nature. It seems that we find it hard to see anything wrong with that which is habit and tradition. We would probably also find it hard to find anything truly wrong with racism if it happened to be the foundation of a habit and a tradition that we all shared, and hear silly attempts to defend it. In fact, this was indeed the case back in the days where using humans of a certain race as slaves was a tradition, and one that was relied upon by certain industries. Fortunately, since the time we transcended this tradition, we have gradually moved further and further away from such racism.
Similarly, the day we go beyond the unnecessary habit we have of eating non-human animals and things from them, and start conceiving of them as sentient ends of moral worth as we should rather than as mere food, we will finally begin being just as horrified and aroused by speciesism as we are by racism today. Without the habit of putting non-human animals in our mouths, there will no longer be any incentive to rationalize unnecessary suffering. This will mark the end of the acceptance of our exploitation of non-human beings, and the beginning of an era where we instead help our fellow sentient beings. Humanity will then go from living off of the bodies, suffering and death of other animals, to living for the purpose of making all sentient beings flourish and free from suffering — regardless of species. That is what it should mean to be human. The day this begins to happen is the day we go vegan, and that is how indescribably important veganism is.