What is a Spirit?

[binary solo]

I think you're pushing sand up hill with this request, OP, since there is no universally agreed definition of spirit as each religious or spiritual philosophy has a different take on it. And then there is the fact that in some philosophies "spirit" and "soul" have different meanings.

For instance, in some philosophies all living things have a "spirit" which is the life force that exists independent of the biological entity. But in those same philosophies only humans have a soul. The main difference is that spirit has no individual consciousness, whereas the soul does have individuality, which remains after the person has died. But these concepts are by no means universally accepted by all people who believe in metaphysical realities.

So given there can be little chance of a general agreement on what is spirit and soul, thern there is little chance of having a meaningful discussion on what spirit and soul does and whether it is detectable or measurable by means of scientific observation and experimentation. If spirit and soul are metaphysical realities, and science is only able to investigate physical reality, then science will never be able to directly observe spirit or soul. Using the instruments of physical science to try to observe metaphysical things is like trying to see radio waves with the human eye. The capability simply does not exist.

There are experiments that can be used to infer something metaphysical, like trying to find out whether the near death experience of floating above your dead body and looking down on the scene is real or imagined. If you are in a controlled space where there is something that could only be observed from above andnot be imagined (like a random number generator on top of someone's head) then if the person experiencing the NDE observes the RNG device this strongly suggests the NDE involved a true out of body experience rather than an imagined / hallucinated one. The problem is it is difficult to create these controlled conditions, so therefore it is hard to test whether NDE's are real or hallucinated. But even then this is not absolute proof, and it also does not explain how the soul or spirit acts or has an effect on the normal living person / creature. All it does is raise more question.