"There's no empirical way for us to determine whether or not spiritual experiences are real," the rationalist will often say, echoing a position long popular in the anthropology of religion and still popular in many academic and non-academic circles.
"What do you mean by empirical?" asks the person who had the experience. "It happened to me, didn't it?"
"I mean measurable," the rationalist will often reply, "by one of your five senses, or by a scientific instrument."
"But when I say I heard a voice say, 'Turn left,' I mean I really heard it," insists her interlocutor.
"How can anyone know you really heard it if no one else heard it?" comes the retort. "If there is no measurable sound entering your ear canal, it's probably just a brain twitch or memory or something else. Who knows?"
"But I was alone in my car when it happened - I don't know if it was just inside my head or if someone else would have heard it too."
"Listen, you may want to get yourself checked out for hallucinations."
"But the voice saved my life - if I had turned right, I would have gotten in the major car crash I saw in my rear-view mirror just after turning."
"Well then you probably already saw the situation getting dangerous and your subconscious just steered you away from it."
"But I didn't even see the intersection clearly yet when I heard it. The situation seemed totally normal."
"The fact that you weren't conscious of it doesn't mean that you weren't picking up signs beforehand."
"Does your subconscious ever sound like a human voice in your head?" asks the person who had the experience with defeat in her voice.
"The brain is a strange thing. We don't even know how it works. I don't rule out the possibility that it could."
And so it goes. This conversation reflects a few common but mistaken presuppositions:
1) Science is the realm of empiricism.
2) Spiritual experiences are totally subjective and unverifiable.
3) When they are verifiable, spiritual experiences are most likely the results of neurochemistry (a brain-deterministic view) or the subconscious (a psychoanalytic view).
4) If a spiritual experience has a positive outcome for the person to which it occurs, it is probably being engineered, consciously or not, but that very person.
These assumptions are quite widespread in our culture among both religious and non-religious people. The first two assumptions, that science is the realm of empiricism while religious experience is not, produce the contradictory claim that experience is not empirical, yet empirical evidence is only that which can be directly experienced. The converse of this contradiction is the blanket trust in empiricism: that everything that earns the label "empirical" counts as solid gold evidence which forms the foundation of Science. In short, these presuppositions create an inability to talk about the evidence of experience itself--namely, how experiences can be evaluated to make different claims about reality. By both dismissing and valorizing experience, the worldview reflected by the presuppositions above labels some experiences as "evidence" and others as "non-evidence."
This labeling often proceeds based on a priori but unarticulated criteria, like "Can this experience be reproduced publicly, in a lab, for everyone to verify?" If not, the experience either must not be real (and if it's not real it can't be evidence!) or it is simply irrelevant to the advancement of human knowledge.
One wonders how this worldview would have dealt with someone like doubting Thomas in the Christian tradition, who would not believe in the resurrection of Christ until he put his own finger into Christ's wounds. Many rationalists would likely say, "His experience was of a religious nature; therefore it is completely unverifiable!" Yet for Thomas, no greater verification could have been provided for his faith. But Christ chastised him for needing that degree of evidence in the first place, believing that he had already, during his lifetime, provided enough evidence for his closeness with God and therefore for the trustworthiness of his promises. What we have here, at the heart of the Christian tradition, is a controversy about evidence--about what God's signs are and what they mean for people living in the world.
Of course, these debates about evidence are by no means limited to the Christian tradition. People rarely, if ever, believe something they consider to be untrue or completely unsupported by any kind of evidence. This doesn't mean that people don't engage in all kinds of complex self-deception about what they do and do not believe; it only means that people rarely will say from a place of full integrity that they trust in a falsehood or a lie. This is why you hear many people stating that myths are "true" even if they know they didn't "really" happen: the myths articulate truths about the world which are larger than the veracity of a particular historical occurrence, and they continue to express those truths in the lives of those who trust in them. Some may even divide "the" world into worlds, arguing that while they myths didn't happen in the world of living human beings, they happened in the underworld, or the spirit world, or another world entirely. These are only two highly generalized approaches to the many ways that people evaluate the truth or falsehood of spiritual experiences.
I would like us to move beyond simplistic understandings of evidence which state that evidence is only that which can be reproduced under the conditions of a controlled experiment. That is one particular kind of evidence--and a very important one--but not the only kind of evidence there is. Before we can start to make judgments about the veracity of people's spiritual experiences, we first have to suspend judgment long enough to listen to their stories and pay attention to the effects those experiences have on the world around them.