What is theoretical computer science?

He says he affiliates a bit with physics. That is what I studied when I was young. Yes, physics attempts to concern itself with the real world. For instance, nobody in their right mind would have anything to do with quantum mechanics if it wasn't how the real world operated. In that sense it seems to me that computer science is much closer to mathematics. The computer is an artificial system constructed to be relatively easy to reason about.

Some people really like the math of quantum mechanics for its own sake.

(See also how (much of) the math for General Relatively was developed without any application in mind.)

The Turing machine is an artificial system constructed to be easy to reason about. The computer on my desk is most certainly not!

'Liking for its own sake' is not quite enough. The first question is whether quantum mechanics would have been invented in the first place if it wasn't for experiments that showed that it was necessary. The second question is even if it was invented, would anyone bother to study anything beyond a single particle wave function? A wave function by itself is not yet quantum mechanics, there is quite a bit of wave mechanics in classical physics. I am quite sure that if quantum mechanics was not necessary nobody would attempt to say anything about a quantum mechanical carbon atom. I.e., a quantum mechanical six body problem. Let alone quantum field theory.

General Relativity much more natural than quantum mechanics. It was mostly created from a theoretical motivation. People were dragged towards quantum mechanics kicking and screaming and it took about 30 years to develop.

Well, it depends. Have you ever considered writing a word processor in a Turing machine?

The Turing machine is a realisation of what a computing machine could be in a logical sense. It’s not so much constructed to be easy to reason about as to be the simplest form of what such a machine could be.

The fact that functions computable with such a machine is equivalent to functions computable in the lambda calculus and Herbrand general recursive functions is the remarkable results.

The fact that it can somehow be linked to an actual computing machines outside of logic is merely a happy accident.

Having said that you could think I disagree with Vardi but the truth is: I think the point he brings is just void of substance. That’s only of interest to people who like university politics and how departments hire. It’s of no impact to the field whatsoever. Why does it matter what is or isn’t semantically TCS and if it is or not mathematics? The problems will still be there the same.

Not a Turing Machine, but with a Lisp interpreter and few atoms (Lambda Calculus in the end) you can state the peano axioms, then a basic arithmetic calculator, and after that, a basic algebra solver in minutes.

https://justine.lol/sectorlisp2/

On Lambda Calculus:

https://justine.lol/sectorlisp2/

Also, the original paper on Lisp it's beauty itself. It's describing Lisp... in Lisp, recursively stating both (eval) and (apply). Magic.