illustration (attribution, if any possible, is at the end of the article)
Buddhism is an evolving set of traditions of expedient means, of teaching devices. Teachers constantly adjusted the teachings to compensate the misinterpretations of earlier teachings… That's why teaching is an important function, and requires an actual and creative engagement, compassionate efforts, not just mere parroting.
Our ordinary minds just love dualism so much though! ;-)
For some, selflessness and emptiness become nihilism.
For others, dhammas become substantial, they are found to have an intrinsic nature (svabhava: fire is not water…) while easily forgetting that such a nature is still conditioned, impermanent, selfless (gplus.wallez.name/8gEEPXJpAp6).
It seems not to matter how many safeguards there are to warn us against these transformations, or how many questions were left unanswered by the Buddha precisely because answers would lead to unhelpful clinging!
The unanswered question about the Buddha's existence after death easily is transformed in a 'no' (by some interpretation of cessation of parinibbana) or a 'yes' (by some interpretation of the trikaya) by later commentaries, traditions, interpretations… then corrected then transformed in the opposite extreme, self then corrected, etc.
To help ourselves get a hold on the unhelpful ignorant tendencies of our ordinary minds, it then matters to see the various teachings as specific antidotes to specific hindrances.
For example, both "lust for existence" and "lust for non-existence" were explicitly listed in the 10 "fetters" from very early on… but they don't automatically call for the same antidote! The Buddha didn't suggest the same objects of meditation to everyone: some people are instructed to get disenchanted with a body they spend too much time and energy adorning, while others are instructed to appreciate this body for the opportunity to embody wholesome qualities and practice towards Liberation…
The teachings, the sūtras, are not some final definitive 'Truth' independent from the context at hand. The unconditioned Dharma cannot be grasped, cannot be expressed in words! What can be expressed is context-dependent.
The unconditioned Dhamma may be pointed to, but not grasped. Just like you can talk of "the universe" but not actually grasp it: you cannot take yourself out of the universe in order to hold it, to 'independently' observe it. You co-dependently arise with the reality you're in, you cannot be taken out without the whole reality disappearing.
And if we see the various doctrines of Buddhism as specific antidotes, specific responses to specific hindrances, then we can marvel at the compassion of the Buddha and of other writers, at their creativity to try and help others… We can feel gratitude, rather than regret the apparent confusion.
How to deal with the contradictions though?
The game is to identify our own defilements, our own confusions, in order to then read the appropriate antidotes ;-) Although not strictly needed, teachers might of course prove very valuable to help us identify such crystallisations and find the appropriate antidotes in the huge corpus of teachings.
To identify our own defilements (so that we can refrain from perpetuating them!) could be said to be the whole point of cultivating mindfulness of our thoughts, of our actions (as manifestations of our ignorance), of our intentions…
The danger is when we read the antidote to the opposite of our views (e.g. we're 'essentialist' but we read antidotes against nihilism, rather than antidotes against essentialism), which will then apparently confirm our errors!
The damage due to "confirmation bias" is constantly under-estimated, the ordinary mind wants to be 'confirmed' in its understanding of the 'truth' a lot more than it wants to "abandon all views" ;-)
But we can use this as a sign in itself: whenever we're a bit too happy to be confirmed in our views, in our understandings, by a sūtra, then it's likely the sūtra wasn't addressed to us!
When a sūtra "confirms" us, the sūtra doesn't support our personal enquiry, doesn't support us to pay attention to whatever has changed since its creation, doesn't support us to realise "by ourselves" the Dharma… When it doesn't question us, the sūtra doesn't act as (the relay of) a teacher, for us to learn something we didn't know yet!
When mere old, fixed words are considered a confirmation of our present self (and how 'deep' our understanding supposedly is), we're just projecting on these words… so that we can appropriate some legitimacy from them. Renewed effort to look again, to enquire again, is then called for.
The Buddha described the teachings as a Raft, to be left behind when appropriate. They are not a Truth to cling to, and therefore there's no grasping of them which would be the "right grasping", the "right clinging".
Clinging is to be abandoned, as per the third noble truth, and "right clinging" isn't found in the eightfold path. "Right view" is not some fixed interpretation of a sūtra that happens to confirm our view, it's not even Buddhism as a whole (since it's just a raft!).
The goal is to see reality as it is… and since it is evolving, no fixed words may ever capture its contingency.
There exist antidotes to what blinds us, specific antidotes for specific veils, and the treatments still evolve to respond to the present circumstances at hand; Buddhism is a live tradition.
But just like there's no medication to be healthy, only medication to respond to what makes you unhealthy, the antidotes of Buddhism tackles defilements, they don't directly cause bliss. Bliss is the cessation of unsatisfactoriness!
When sūtras confirm our understanding, it's like taking medicine for a disease we don't have. First, it won't help to solve the defilements we do have. Second, it might even poison us! Medicine is not meant to taste nice, it's meant to heal: it doesn't have to be hard-going, but an "antidote" shouldn't point that "everything is fine with me"… or it's not an antidote at all! We might even become dependent (just like some people become dependent on antidepressants) rather than free.
Buddhism is challenging. It's meant to be, so that we learn something new, something other than the ordinary perpetuation of habits, of certainties, of "I know better (because…)", of contentiousness and trying to impose our views on others.
All these sūtras contradict one another! The path is in saṃsāra, it's unsatisfactory (gplus.wallez.name/AmuTinzujq8): our minds wish for clear truths, easy truths (for which we don't want to study a PhD, because we have "other things to do"…) but that's not how it works.
The contradictions are on purpose, and they're not so much between sūtras, they're between our prejudices and their antidotes! The sūtras are the set of antidotes, not 'health' itself. Dharma gates are innumerable: the gates aren't Nirvāṇa itself.