The Philosophy of science limits scientific investigation to things that are collectively verifiable via our sensory systems using technology and tools that expand their range.
As an example, if we all went into the woods at night, and one person heard a unique sound, but nobody else hears its, that sound would not be part of the verifiable data, since nobody else could hear it. The method of science has peer review as well as independent verification of experiments to make sure the data is tangible and objective to all. Anything beyond this is not allowed.
That being said, there is a range of real and tangible data, connected to consciousness, that is not consistent with this philosophy. For example, say I had a dream and related the dream in all its tiny details. Even if my recollection was spot on and I had the reputation of always telling the truth, this dream is not verifiable by anyone else. Nobody else can read my mind and then verify my claims using their sensory systems. We do not have the tools, so I could externally record my dream details, nor could I reproduce this particular dream on demand, even if we had the tools. Dreams are often one of a kind.
The dream is an example of real objective data, to any first person observer. We have all experienced, dreams to know they are real output data from the brain. However, since any dream is not verifiable in a collective sense, it is called subjective to the collective mind. Dreams exist at the threshold of where the philosophy of science starts to break down in terms of the group, but not necessarily in terms of the individual. You can record and analyze your dreams in a solid scientific way, but this will never be verifiable in terms of the group.
If a person had a spiritual experience, this may also be a unique event, with respect to its details. It may be a one shot thing, that may never occur again, in the exact same way. This will often be verifiable in terms of the philosophy of the science of one, but not the philosophy of all. This does not mean it was not real data, but only means it is outside the boundaries of peer review and collective verification science. The human psyche is the last frontier for science, but its collective investigation would require altering the philosophy. Nw it called soft science due to being at the boundary.
Before the age of enlightenment; age of reason, the philosophy of science was more expansive and took into account projection from the human psyche. Science was originally more mystical.The alchemists, who would develop many of the tools and procedures of modern chemistry, made use of the unconscious projection factor; mysticism. They were able to develop tools and methods, using unconscious development factors that are not easy to verify; science from not science, based on the modern philosophy of science.
When I was a young development engineer, I was given an emergency project that required I develop the best available technology for removing mercury from water. I had to meet EPA standards ten years in the future. To meets the need of the emergency situation, I needed it done, yesterday.
There was nothing in the science literature to borrow, since I had to exceed the state of the art by an order of magnitude. At that time, I was also doing independent hobby research on the human psyche and I had become an expert in collective human symbolism. I decided to try an alchemist mystical logic approach, instead of try random tweak experiments, using the then best existing science and technology.
The alchemists were very much acquainted with mercury and had logic of like attracts like. To make a long story short, using their approach, modified to the future, it took me three weeks to demonstrate the new best available technology. I even wrote my alchemy logic approach, in a paper that I asked to publish a few months later, due to the successful scale up and demonstration that treated millions of gallons of water to below 1 part per trillion.
Everyone rolled their eyes when they read my paper, but since I got the job done, in record time, under budget, it was all acceptable, in light of the quirks of a young eccentric hot shot scientist. I was jokingly called the Mercury Man; quicksilver.
The point is, there is a broader based philosophy of science, that is not allowed by the current method, unless it can produce tangible results, or be covered up with alternate logic that is less metaphysical. I pushed the boundary of the philosophy to be 100% honest. Someday science will expand to include this, so we can calibrate the most important tool in science; mind. Without this gray area of science developed, mind calibration is not possible. In the mean time, mutually exclusive theory, which is not rational, is accepted and even published. Alchemy exists in modern theoretical science, but only if properly disguised with math.