What's The Guarantee That Other Human Beings Exist?
The criteria for evaluating any such ideas is the basis of their arguments. Mere conjectures do not necessarily pertain to truth because there is no limitation to human imagination. Once we understand human sources of knowledge and their limitations, we must form any ideas only on their basis. Please also refer to the video below from 1:16:04 to 1:22:57 https://youtu.be/ysn4SDfKlVA?t=4564