As I understand it the patent is only valid if it shows that the idea can be reduced to practice.

Someone got a patent for a warp drive [1], so I don't think being actually possible is a requirement for patents.

[1] https://patents.google.com/patent/WO2001057881A1/en

No. It must be novel, non-obvious and "useful", which obviously was considered to be fulfilled by the patent office. The patent describes how the invention can be used instead of tubes.

Doesn't there need to be a preferred embodiment? Not debating, just curious.

I have not studied the content of the patent, but the "Cited by" list includes the Who's Who of the industry; so the invention is apparently relevant.

I believe the you have a different definition of "invented" than the author and myself.

Those sources appear to exclude Lilienfeld. He didn't create a good or tool. He didn't create a material. He didn't create a manufacturing process or a control procedure or a method of measurement.

Lilienfeld was a brilliant man but he didn't invent transistors any more than Albert Einstein invented gravitational wave detectors.

The patent doesn't mention the term "transistor"; but obviously the patent office came to the conclusion that it is a patentable invention, and the cited by list confirms that it is considered a relevant invention by Bell Labs and other notable institutions. Prior art by Lilienfeld did even stop some applications of Bell Labs from going forward. The transistor invented in 1947 was a point-contact transistor, which is not the concept applied in micro processors as the article confirms.