Can someone please explain to me how does one creates new technology without having alt least one of the following? a) working prototype, b) consistent theory w

Can someone please explain to me how does one creates new technology without having alt least one of the following? a) working prototype, b) consistent theory why the new technology will work. In other words, what made Roger Shawyer believe his engine will work if he does not know how should it work nor have a prototype?