There's no transaition from one to the other. Otherwise we wouldn't still have agriculture and industry.
I never said previous sector being completely destroyed after each transition. Just number of employed people falls to insignificant numbers (e.g. there is still agriculture in the U.S., but it provides just 2% of jobs).
It's not faith, it's how things are actually working in the real world, right now. It's as much of a theory as any other science theory, like the theory of gravity. Automation, efficiency, things getting cheaper, and everything else. Just because you don't see it doesn't mean it doesn't exist.
May be it is true for few products like electronics and IT, but for the most stuff its completely false! Houses, education, healthcare, energy,
food (agriculture already automaded by 99% now!) don't show any signs of price reduction and even opposite if we count median workers' wage (which is falling due to automation and offshoring).