As a child, I considered giving up meat several times but was persuaded not to by the argument that by eating meat I was responsible for the existence of farm animals in the first place, and that it was better for them to exist than not to exist. I was also persuaded that veganism was fatal, so I didn't go there. It was rare for people of my acquaintance even to be vegetarian at that point.
The first person I met whom I was aware was vegan was a first year medical student at university. He was lactose intolerant so his motivation was not ethical. Also, at the time I was only aware of the idea that one should be vegetarian for reasons of avoiding suffering and killing directly, which I didn't consider sufficient, probably for reasons of cognitive dissonance. Cognitive dissonance is the difficulty of holding two apparently contradictory ideas in your mind at the same time, which many people avoid, perhaps as part of human nature. Since I ate meat, I didn't let myself belief that suffering and killing was relevant.
As time went by, I met other people I knew to be veggie, and found that their reasoning was often not based on the argument that it involved direct suffering and death but on the tropic levels argument. That is, if you eat food that has been running around or flying, it will have burnt off a lot of energy which food which has not moved much won't have done, so it will itself have needed to have eaten a lot of food which is less active, commonly known as plants. Therefore, why not just cut out the middle stage and eat plants directly? I was intellectually persuaded by this argument but not enough to change my behaviour.
Later still, I read Peter Singer's 'Animal Liberation' along with some other books, as part of my first year philosophy studies. These were enough to make me feel extremely guilty about eating meat although I drifted along in the momentum of what I'd always done for a bit, as people do. At this point there was an emotional element to my difficulty in not being vegetarian but it still wasn't enough to persuade me to give up meat. I was also persuaded that veganism was the aim and lacto-ovo only a transitional state on the way to a better goal, something I still believe.
However, what really clinched it for me was when my friend Debbie came to visit. We were about to go to a pizza place (clearly at that time at least and probably still, cheese in pizza chains wouldn't have been vegan but I'll leave that aside for now) and looked on the menu, planning to buy a pizza between us. I thought about how much it would annoy my friend if I were to go veggie at that moment and consequently that's exactly what I did. It was the evening of 9th March, 1986.
Once I'd done that it took me some time to become assertive enough to refuse meat as such. I found myself not eating the meat I was given but still accepting it, leading to a rather unbalanced diet consisting of the two veg without the meat, although this only went on for a couple of months before I started cooking for myself all the time and therefore just eating a mainly vegan diet with a bit of dairy in it. I went vegan about a year and a half later. This is an example of how you can let others down by not being assertive, something which I need to bear in mind. If you don't stick up for yourself you can hurt others.
What was interesting about this process, though, was the way my opinions changed in spite of the immediate reason for changing my diet simply being to annoy Debbie. I then became much more easily persuaded of the health-related and ethical arguments for giving up meat, particularly the tropic levels one, and became somewhat proselytising on the matter as converts often become. It was no longer hard to believe that it would be better for farm animals not to be born than to exist in the way they currently do or that the environmental havoc wrought by livestock farming harmed other human beings such as the ones living in rainforests. I no longer had an emotional investment in eating meat, so I no longer believed what I previously believed.
Here, of course, is where the problem emerges. I changed my behaviour and adopted a new belief system while rejecting the old one. What I could be said to be doing here is what other human beings do. I am resolving cognitive dissonance by choosing the arguments which support what I do. I don't know how to decide what's outside this kind of way of thinking and for a long time I believed that was all there was.
Jumping forward a few years and you find me sitting in a seminar room with a Women's Studies tutor looking at Simone de Beauvoir and Jean-Paul Sartre. My aim in pursuing this line of studies was based on the idea that patriarchy is the origin of all the world's ills. I proceeded to say something about other species based on de Beauvoir's rather peculiar approach to interpreting sex roles in angler fish and bees, and that tutor announced that she absolutely was speciesist because she believed consciousness was based on language and not an innate property of the central nervous system. To put it another way, if you have no voice, you have no rights and you don't matter. Later still, I read 'The Sexual Politics Of Meat', which is an interesting read with which I substantially agree but makes the remarkable claim that it's notable that many feminists are also vegetarian and that there is a link between the two. In fact, my experience is quite the opposite. To me, it's remarkable how few feminists are vegetarian, and I find this quite worrying because it makes me wonder how compassionate people in general really are. You have to be quite remarkably numbed to suffering and empathy to be unaware of the suffering of other mammals and birds, and when I think about the language-centred approach of the view expressed above, it strikes me that people very often just believe what they want and use arguments to back up their beliefs after the fact, so they don't feel the need to change.
Of course, it is also the case that many feminists are vegan but just as veganism should be an unremarkable position, it should also be entirely unremarkable that feminists are vegan. However, in my experience they usually aren't and that's because like myself, they choose arguments to justify their position rather than using them to improve it.