logical fallacy: denying the antecedent
The question is not whether syntax "guarantees" the presence of semantics, but whether it "could be" sufficient for implementing semantics.
fallacy of destroying the exception
Just because some instances of simulation are not duplication doesn't mean that every instance of simulation fails to be duplication.
syntax/semantics distinction for programs is different from syntax/semantics distinction in cognition and linguistics
Syntax is not semantics.
Syntax by itself is not sufficient to guarantee the presence of semantics.
Simulation is not duplication.
There is a difference between "simulating a brain" and "duplicating a brain".
incoming strings are pattern-matched against a catalog of patterns, and an appropriate reply is selected
metaphor, "Prices are increasing.", "Prices are rising.", "Prices are like a moon rocket.", "Prices are like a Concorde taking off.", "Prices are like a helium balloon cut loose."
You can't understand language without "semantics"; you need a model of the world.
You need (linguistic) semantics; (linguistic) syntax is not enough.
Linguistic semantics can be implemented via syntax, since arbitrary computations can be implemented via syntax (cf. Church calculus)
When Searle came up with his argument, AI consistent of rule-based expert systems and non-statistical NLP.
AI and NLP probably requires some pretty good internal modeling of the real world.
"Imagine putting a football on top of a brick and tapping the football in different places; what might happen?" "Imagine putting a hungry cat and a hungry weasel into a cage. What happens?"
"The man in the room doesn't understand Chinese, but the system composed of the room and the man does."
"The Chinese room can't understand language because it lacks embodiment. If you put the computer into a robot body, it can learn semantics."
"The Chinese room just has the wrong structure. If, instead, we simulate neurons and the entire brain, then the resulting simulation can understand."
Humans are computers.
Humans can think.
Therefore, computers can think.
The brain is a machine.
The brain can think.
Therefore machines can think.
No obstacle "in principle".
May be able to build thinking machines out of "substances other than neurons."
Only claim that this can't succeed by building "a certain kind of computer program."