My friend Ellie is transgender. When Ellie and I had coffee a while back, she told me that ever since she was little, she just knew that she was a girl. This wasn’t based on any medical or scientific evidence—it was based on simply turning inward and examining her own sense of self. Some of you will sympathize, others will scoff, but both Ellie and I appeal to the evidence of experience and introspection to support deeply held beliefs. How do we evaluate such claims?

Ways of Knowing

Well, consider first that everyone relies on introspection as a source of knowledge. Introspection is one of the chief ways we come to know things. It is how I know that my knee hurts, that I am feeling sad, or that I exist. There are other ways of knowing, such as testimony, perception, inference and memory. But my experience of my own internal self is a perfectly legitimate means of knowing. Compare introspective experience with perceptual experience, for example. By perception, I can know that you feel depressed—I see your face, I listen to your story. By introspection, I can know that I feel depressed. So we all depend on introspection as a source of knowledge.

But like all sources of knowledge, introspection is not 100% reliable. The man who (by introspection) believes he is made of glass or believes he is a chicken, is mistaken. These claims easily allow for falsification, based on accepted definitions and considerations about what is or isn’t possible. It is physically impossible for me to be made of glass, and it is logically impossible for me to be a chicken, given a certain definition of ‘chicken.’ The clear definition provides a means of falsification.

The Difficulty

What about cases of religious experience and transgender identity? These are difficult, if not impossible, to falsify. Gender claims don’t submit to falsification by way of definitions, for instance. ‘Male’ and ‘female’ resist being cast in strictly biological terms. If we could simply assert that “female = having two X chromosomes,” then it would be simpler. But women with Complete Androgen Insensitivity Syndrome (CAIS) have a Y chromosome. It is also possible for a male to have two X chromosomes. Even genitalia can be ambiguous. So the precise definition of ‘male’ or ‘female’ remains slippery. If we insist on a rigid definition, we will still need to create new categories for those who do not fit in the boxes. Even in the religious realm, a place where strict categories are often assumed, Jesus himself said that “there are eunuchs who have been so from birth.” (Matt. 19:12)

Claims of religious experience and gender identity are also difficult to falsify because they involve private, internal experiences. When I first encountered God and came to believe in him, my experience resembled what people might call a vision or epiphany. Powerful emotions and a sense of “rightness” also accompanied the experience. I can tell you about it, but I cannot share it with you directly, the way I can share my lunch with you. And since only I had access to this experience (or now to the memory), it cannot be falsified (except by me, perhaps). (It could still be undermined in various ways, though.) Similarly, when someone suffers from gender dysphoria (the feeling that one’s biological sex does not match one’s gender), doctors must rely on the self-reporting of private experience to make the diagnosis.

Responding Respectfully

So how should the reasonable person respond to a friend who makes such a claim? Unfalsifiability is not enough to dismiss these claims—my claims about being in pain (which seem legit) are similarly unfalsifiable. But I admit that some moderate skepticism is epistemically healthy. I would want to know more about their experience. Are they generally trustworthy, reliable and reasonable? I would want to know that their mind is functioning normally. If it turns out that they suffer from some physical or psychological disorder that undermines the reliability of their mind in general, then this should probably lower my confidence in the veracity of their claims. An atheist friend of mine dismissed his own religious experience after he was diagnosed with a form of epilepsy known to sometimes produce similar experiences.

But if you don’t have any reason to think your friend is unreliable, then you should probably say to yourself, “Well, they have a good reason to hold their view. They aren’t crazy. I may not agree, but they seem to be thinking rationally.” If you consider your friend to be especially reliable, then you may even think, “Well, perhaps their testimony now gives me a good reason to believe that such things are possible or even true!” Their word may not be enough to tip the scales of belief for you, but it should at least move the needle.