Can Machines Think?
In 1936, Alan Turing wanted to answer a question in pure logic. He invented an imaginary machine so simple it could not be misunderstood — and accidentally defined the modern computer.
The universal machine
A Turing machine has a tape of symbols, a head that reads and writes, and a fixed table of rules. That is all. Yet Turing proved that one machine of this kind can simulate any other: the universal machine. Feed it a description of another machine and it will run it. That is why your laptop is general-purpose.
Computability is the boundary this draws. Some well-defined problems simply cannot be solved by any machine — the most famous being the halting problem: no program can decide, for every possible program, whether that program will eventually stop. Not “we are not clever enough yet.” Proven impossible, forever.
The imitation game
Turing replaced the unanswerable question “can machines think?” with a testable one: if a machine’s conversation is indistinguishable from a person’s, on what grounds do we deny it thought? The Turing test is not a definition of intelligence. It is a deliberate move away from definitions and toward behaviour.