Here are some examples:
Inklings and intuitions
Convictions, beliefs
Proven facts
When talking about knowledge we tend to value the proven facts. The rest is usually discarded as vague and unsubstantial.
In the spiritual field proven facts are rare. There is still no scientific instrument able to measure the size of a chakra for instance. Everything we know about levels of consciousness, the spirit or human destiny comes from inner experience, intuitive perceptions, or transmitted teachings.
Working with a scientific approach based on physical measurements, parameters or facts simply does not work on the spiritual level. Most of what we "see" or perceive from the inner worlds has never been measured in a scientific way.
So what are our tools? Logic still works of course. Common sense is essential as well. But most of all, our real tools are our feelings and intuition.
Feelings and intuition are very powerful and our best allies in this inner exploration. These mind skills can be developed greatly, a bit in the same way as our physical senses can gain in refinement and substance.
Taking the line of exploring the physical facts can be seen as a lost cause.
Entering into polemic discussions is usually counterproductive. We have to accept the fact that at this stage, there are many truths as there are spiritual experiences. If some beliefs, intuitions, inklings or spiritual models are not 100% correct, they might still provide a mind frame which can be used for the time being.
As Djwhal Khul puts it, "simply use what you need and discard what you don't need...".
Simply remember that this is the mind frame in which we evolve in the spiritual field. Spiritual knowledge is not based on measured proven facts. Spiritual knowledge could be called as well "touch knowledge" where you integrate or reject inklings by the way they impact on the surface of your mind.