Well not sure you’d call them tenets. But many would say the most central teachings of Buddhism are the four noble truths.

To understand these you need to know what “dukkha” means. It’s often translated as “suffering” but also as unsatisfactoriness, anxiety, stress. But, though those are all examples of dukkha, none of them are really good as translation. We don’t really have a word corresponding to dukkha in English.

That’s because it also includes unblemished but transitory happines! Even if you are happy without a cloud on the horizon for years on end - you aren’t suffering, no anxiety, no stress, nothing like that, but it still counts as “dukkha” because you haven’t established a happiness that will last for ever. So, even though you may not see it that way at all, you haven’t solved all your problems for all time, and haven’t achieved a permanent state of happiness, so in that sense it is “unsatisfactory”. It doesn’t mean at all that you have to be miserable or feel that any happiness you experience is inadequate. But just to recognize that it has this temporary nature to it and that it’s not a true happy ever after.

So with that background, then the four truths are

1. the truth of dukkha
2. the truth of the arising of dukkha
3. the truth of cessation of dukkha,
4. the truth that there is a path leading to the cessation of dukkha

These are not tenets though. No point in taking them on trust. They are things to investigate and which you may eventually come to see for yourself.

I think it’s best to just send you on to Walpola Rahula’s book “What the Buddha Taught” to explain those truths in detail, if you are intersted to find out more. He was a renowned scholar, expert in the Pali Canon, the early Buddhist sutras, and this book is one of the most highly regarded books on Therevadhan Buddhism in modern times.

The Four Noble Truths - Walpola Rahula: What the Buddha Taught

He taught many other things, and then more things are attributed to him in the more recent “Mahayana sutras” written about half a millenium after his death. These are accepted as “canon” by the Mahayana schools of Buddhism. While the Therevadhans accept only the earliest teachings as canon.

But this teaching is central to all the schools of Buddhism. And the interesting thing about it is that unlike most religions, there is no need at all to affirm any creed.

So that makes it hard to answer a question about “what are the main tenets”. Buddha taught many things, but none of them were tenets, there is nothing you have to accept on faith because he said so, or because any other sacred text said so. There is nothing you have to recite to say “I believe in …” as you may be required to do, for instance as a Christian.

All that is required to follow the Buddhist path is an open mind, and a faith that these four truths are worth investigating.

Sometimes people will say you have to believe in rebirth to practice as a Buddhist, but that’s not true. Though he gave many teachings on rebirth, he made it clear that there is no need, or even value in affirming belief in things you can’t see for yourself. And few of us are able to see rebirth through our own direct experience. So you are not required to believe this as a Buddhist :). It does help though to have an open mind about what happens when you die. Because if you decide “when I die that’s it” that’s affirming a belief too, cutting off various possibilities as things you won’t even look at. As a Buddhist, following the path to truth, then it’s best to have an open mind about what happens when you die, or indeed about what happened before you were conceived, or anything else that you don’t know directly and clearly from your own direct experience.

There’s a ceremony you can take part in during which you affirm to the world that you are now a following the path of the Buddha. Which you may have been doing already, but now you make a strong personal commitment to the path.

Unlike most such ceremonies in other religions, you are not required to assert that you believe anything to “become a Buddhist”. Instead you commit to following a path of open discovery. You commit yourself to opening out to truth, whatever it is. And, it doesn’t mean you become a perfect person. You just are following a path, and made your first steps onto a path.

Trungpa Rinpoche wrote about this:

“If we adopt a prefabricated religion that tells us exactly the best way to do everything, it is as though that religion provides a complete home with wall-to-wall carpeting. We get completely spoiled. We don’t have to put out any effort or energy, so our dedication and devotion have no fiber. We wind up complaining because we didn’t get the deluxe toilet tissue that we used to get. So at this point, rather than walking into a nicely prepared hotel or luxurious house, we are starting from the primitive level. We have to figure out how we are going to build our city and how we are going to relate with our comrades who are doing the same thing.

“We have to work with the sense of sacredness and richness and the magical aspect of our experience. And this has to be done on the level of our everyday existence, which is a personal level, an extremely personal level. There are no scapegoats. When you take refuge you become responsible to yourself as a follower of the dharma. You are isolating yourself from the rest of your world in the sense that the world is not going to help you any more; it is no longer regarded as a source of salvation. It is just a mirage, maya. It might mock you, play music for you, and dance for you, but nevertheless the path and the inspiration of the path are up to you. You have to do it. And the meaning of taking refuge is that you are going to do it. You commit yourself as a refugee to yourself, no longer thinking that some divine principle that exists in the holy law or holy scriptures is going to save you. It is very personal. You experience a sense of loneliness, aloneness—a sense that there is no savior, no help. But at the same time there is a sense of belonging: you belong to a tradition of loneliness where people work together.”
…

“You take refuge in the Buddha not as a savior—not with the feeling that you have found something to make you secure—but as an example, as someone you can emulate. He is an example of an ordinary human being who saw through the deceptions of life, both on the ordinary and spiritual levels.”
,,,
Then we take refuge in the teachings of the Buddha, the dharma. We take refuge in the dharma as path. In this way we find that everything in our life situation is a constant process of learning and discovery. We do not regard some things as secular and some things as sacred, but everything is regarded as truth—which is the definition of dharma. Dharma is also passionlessness, which in this case means not grasping, holding on, or trying to possess—it means non-aggression…” The Decision to Become a Buddhist