How do we know attaining complete liberation from dukkha is possible?
This is a question I’ve made to myself in multiple oportunities, especially after having explained the basics of (what I understand about) the Dhamma to people not acquainted with it. When in such circumstance, I interpret that thought (the question) not necessarily as doubt in the Dhamma, but as a question of “common-sense”.
I have my own arguments that I’ve been buiding over the years about why I think attaining Nibbana is possible, but ultimately, it seems to be just a statement coming from faith and from the extension of a principle that until now has proven to be true, logical, compatible with evidence and useful (namely, the idea of the dukkha as a consequence of tanha, and that the diminishing of the presence of tanha leads to the diminishing of the presence of dukkha).
But, what does assure us that such principle could be applied until the complete eradication of dukkha?
It’s like thinking that just because the scientific method has shown itself to be useful in -apparently- understanding some aspects of reality (based on our ability to use the information gained through the application of the method to predict outcomes, to built technology to achieve some ends, and the ever growing power to keep understanding more and subtler aspects of nature), that would necessarily mean that understanding everything about reality is possible. Personally, I don't think that's the case, because I consider the possibility of reaching a point where our technology does not "expand" enough the power of our senses (i.e., we reach a practical limit of detection of events or presence of some entity or phenomenon), or that there could be stuff in Reality that do not interact with the things we can effectively interact (no matter how subtle or indirect the degree of interaction with such phenomena).
Could it be the case that there is a physical, biological or spiritual (whatever that could mean) condition that could limit the application of the Buddhist method to the very end, just like what could happen with the application of the scientific method?
Just in case, I don’t see any problem admitting to myself that faith in -what the suttas tell us about- the Buddha and in my own experience is what keeps driving me forward in this path. I think that science is not that different in this regard: through inductive reasoning, and assuming the reality of an external world, the possibility of knowledge of (at least) some parts of it, and the regularity of events, faith (or confidence in the reality of the assumptions) seems to be an useful principle when investigating nature.
So, the question can be formulated as such: what is the epistemic justification for having confidence on the possibility of complete eradication of dukkha? One can have confidence, but based, for instance, on this definition of knowledge, how can we justify the belief about the possibility of Nibbana, beyond inductive reasoning and confidence?
I think this question could be particularly beneficial for putting to test the recurring idea of both Buddhism not contradicting knowledge gained (or possible to be eventually gained) through empirical means, and Buddhism as a “science of the mind”.
I’d love to here your thoughts on this.
EDIT: There's an ongoing discussion on this same question of D&D-SuttaCentral. There are very good answers and feedback in my opinion. If you're interested, here you'll find the thread.