Evidence can be gained through a variety of means. Just as you would wish to use a sensitive detector of particular frequencies of light if you are doing x-ray crystallography, and not, say, an acoustic detector, so too we need to develop and use detectors that are appropriate to the realm in which we wish to gather evidence if we are to hope to gain any knowledge in that realm.
Thus, if we wish to develop knowledge of spiritual realms, we will need to develop organs of perception (for no material ‘device’ can do this for us) which are capable of perceiving in the realm of the spirit. Not only that, but those organs, like any physical detector, need to be sensitized, tuned, and placed in the proper experimental setup for good evidence gathering to be likely.
Of course, the basis for the spiritual organs of perception we are talking about here are rooted in our attention: it’s quality and rhythm. For example, we lay people can only talk about all the fascinating stuff coming out of quantum mechanics in a second-(or third)-hand way, because we have ourselves not done the experiments in question, and our judgments and opinions on the matters are derivative of the interpretations of these experiments by those who have done them and their interpreters. We would not expect an interested lay person to provide new information about quantum processes ex nihilo, but we can learn to conceptualize and come into closer relationship with those processes by virtue of our studies of what has been communicated about them by relative authorities.
The exact same holds for spiritual considerations: those that have developed capacities to perceive spiritual realms can interpret and communicate these results to those of us that don’t, and we can study and learn about realms which we may not otherwise have access to as a consequence. Moreover, just as we might, if we were really interested, take the necessary steps to learn the skills and concepts necessary to do research in quantum mechanics, so too we can take the steps necessary to learn the skills and concepts that allow one to do research in the spiritual worlds.
Or does all this sound completely far-fetched?
Unless we are scientific researchers in a particular field, we actually have very little direct evidence for our knowledge about quantum mechanical processes, chaos theory, and so forth; it’s almost completely anecdotal, yet we trust those that have done the research to provide us with a coherent and accurate picture of ‘what it is like’, and primarily on this basis we feel comfortable using the concepts and talking the talk.
I’m only writing this because I wanted to point out that the scientific method in no way whatsoever excludes the non-physical, and that it is possible to have a clear understanding of how that is so; i.e. such a thing as spiritual science is possible. Poor research is just as much of a problem in physical science as in spiritual science — and we must either rely upon ‘experts’ to let us know when this is the case or become an expert ourselves.