Kant has said that there are some questions which should never be aske — Solipsism

"Solipsism need not be positive, it need not assume any burden of proof. The defender of solipsism may proceed as follows: "You mistake my purpose; I am not trying to prove the truth of solipsism. I say merely that the situation is ambiguous and capable of two explanations, and I see nothing but sentiment which obliges me to reject the solipsistic one. ...logically we are left with a sort of negative solipsism on our hands which we can not get rid of. Actually we simply toss it away. We can not stand that kind of suggestion. Our whole being rebels. We simply banish solipsism out of court. But I submit that this is not a logical nor a philosophical way of escape."

"Solipsism... is sometimes spoken of as the philosophical term for insanity. It certainly seems to stand for metaphysics run mad, or, in politer language, for subjective idealism carried to extremes. The solipsist claims to be the sole inhabitant of the universe, and all manifestations to the contrary are merely subjective states of his own. As with so many other mentally unbalanced persons, his cosmos is all ego."

"Solipsism has no real ground to stand on and the pragmatist is the very last in the line of those who may be accused of even seeming to have taken, or to have tried to take, his stand there."

"If I felt reckless or strong enough to shoulder the responsibility, I might not object to a solipsism that made me the all by emphasising the inevitable relation of experience to an experient; the trouble comes when other experients claim a monopoly of this relation in the face of conflicting claims, and propose to reduce me to incidents in their cosmic nightmare."

"The argument in favor of Solispsism, put most simply, is as follows: "I cannot transcend experience, and experience is my experience. From this it follows that nothing beyond myself exists; for what is experience is its (the selfs) states." The argument derives its strength, in part, from false theory, but to a greater extent perhaps, from thoughtless obscurity."

"What is hell? Hell is oneself. Hell is alone, the other figures in it Merely projections. There is nothing to escape from And nothing to escape to. One is always alone."