[nitrogen]

However it does not follow that the scientific method is the only way to knowledge. It also does not follow that all true knowledge, or even a fraction of it can be acquired through the scientific method.

We would have to agree on the definition of "true knowledge" to come to a complete understanding of each other's positions, but I'll take a stab at justifying my opinion that science is the only possible source for all "true knowledge". I'll define "true" as empirically tested and repeatable by others, and "knowledge" as statements about something tangible (e.g. brains), or about intangible concepts embodied within tangible things (e.g. brains thinking about ideas).

One needn't fully accept these definitions for the argument to hold, if one accepts that personal experience is a source of personal knowledge. Basically, if we consider all the claimed sources of knowledge, and consider which "way" of knowing applies in the most places, gains the most new knowledge over time, and has the best track record for producing societal advancements of knowledge and technology, the only "way of knowing" left standing is science.

You also mention "life purpose" and "knowledge is good" as counterevidence to science. But scientifically speaking, there is no objective purpose or objective good. There is only natural selection favoring the evolution of a desire for knowledge. That desire can be studied scientifically via neurology and related disciplines.

[JackFr]

Ultimately, your 'justification' is just an assertion that if it doesn't come via the scientific method, either its not true or its not science.

I wouldn't call the idea that "Knowledge is good", wisdom is better than ignorance, and freedom is better than slavery, etc. counterevidence. But I believe they are true things which I cannot prove via any sort of experiment, in particular because 'good' and 'better' are of necessity subjective.

[nitrogen]

I don't think you can dismiss my line of reasoning by saying "ultimately" and then saying something I didn't say at all.

It seems that we indeed cannot agree on a useful shared definition of "true". The laws of physics are ultimately indifferent to our notions of truth, and yet our notions of truth are instantiated as emergent phenomena within physics.