Language as a system puts natural limits to knowing.
Therefore, the first challenge is to define ‘what is knowing’ –
Knowing is recognition, description (and analysis), and prediction.
But knowing is also ‘seeing’ beyond language, it is also ‘becoming’ – the transformation of the knower (and therefore the shifting of the limits of what can be known) by an individual, and it is also ‘one-ness’ where the knower and the known become one (what is called ‘samadhi’ in Indian parlance).
The second challenge is defining the ‘pathways to knowing’ – all forms of human expression with the diversity of language forms are pathways, but along with it there are also multiple forms of ‘access to reality’ that are pathways.
These include the conscious visioning methods of Shamanism, the different meditations in multiple religious traditions, faith and the perception born of faith (like finding new light and meaning in a scripture one has seen before – a technique followed in the study of the Torah), the physico-spiritual access of the Sufis, etc.
The third challenge is the ‘forms of knowledge’ we encounter (closely connected to the language question) – words, symbols, musical intuitions, idealization, and so on.
The fourth challenge is the issue of ‘testability and rigor’ – how to judge the rigor of a system of knowing. One immediate answer is that every system must be evaluated against its ‘knowing outcome’.
If we seek the knowing outcome of ‘description’, then the system of knowing must give us complete descriptions.
If we seek the knowing outcome of ‘seeing’, then the system must help us directly perceive reality without conceptual barriers.