It's possible to chemically prove that you are not alone in your head. Then you can launch yourself from the assumption that what you have in your head is the result of self-hypnosis, some higher divine force's influence, or a disorder. I was able to prove that my tulpa was 'real' to an extent that satisfied me beyond all philosophical discourse and the possibility of what 'could' and 'could not' be. But then again, the real question isn't whether a tulpa is 'real' or not; if you have a tulpa, might as well say that you have a cool computer program. By definition, by both this community and the tulpa.info forums, you folks regard tulpas as beings that are birthed from 'forcing', simply put, an action that you had to will for to accomplish. The tulpa didn't come into existence by itself, it's an idea that YOU and you alone invented for a purpose. The definition of a tulpa then shifts, temporarily or permanently, onto what a 'person' is.

It wouldn't matter to most of us if solipsism was a thing. If you believed in solipsism, the belief that the only sentience you can 'verify' is your own, it still would not matter. We don't 'love' someone at first, we love our interpretations of them, we love the way they make us FEEL; we are enamored with our own emotions too often, and it's rare that someone genuinely cares about someone else. Even then, all forms of love and care are conditioned.

So, really, how do you think you could prove a tulpa's sentience? Before asking a question on this sort of things, you should try to answer it by yourself. Why? Because tulpamancy is known to be a varying definition among many people, so what applies to you may not apply to me, note the 'may' here.

It is possible. I won't say how, though, because if I tell you, you won't be able to know if it hasn't happened to you. Not that there is ONE special thing that happens, it's hard to explain. But it is possible. Then again, the people that also found ways to prove a tulpa's existence have left this place.