In George Orwell's essay, "Politics and the English Language," is the following a metaphor, a similie or neither:
"...one often has the curious feeling that one is not watching a live human being but some kind of dummy..."
Quote: (page 6, paragraph 12)
Let's start with definitions. A metaphor is a figure of speech. It is not literal in meaning. A metaphor uses two unlike ideas or expressions and replaces one with the other while drawing a comparison between the two. For instance, hams are round and heavy and don't move. People who sit and do nothing might be compared to ham. A metaphor might make that comparison: Sam is a ham. [Actors are also called "hams," but we've invented a new metaphor using "ham."]
A simile is a figure of speech. It is not literal in meaning. A simile uses two unlike ideas or expressions [this is where it starts to be different from metaphor ...] and compares one to the other by using the words "like" and "as" [a few others too, but these two are most common]. For instance, a rose is fragrant and beautiful. A well cared for cat is fragrant and beautiful. A simile might show that comparison: The kitty is like a rose. To illustrate further, the metaphor above might be turned into a simile: Sam is motionless like a ham.
An analogy is a literal statement. An analogy does not have a figurative meaning. It is literal. An analogy presents a literal statement of how two things are like each other. For instance, the ocean's roar is loud. The roar of traffic is loud. An analogy states that similarity between the two: I have a mistaken feeling that the roar is heavy traffic when really the roar is the ocean tide.
"the curious feeling that one is not watching a live human being but some kind of dummy"
The quote you list is an analogy. The statement evokes a mental image but both parts are literal. No part of it is a figure of speech. It is not a metaphor. There is no substitution of one idea or expression for another. The human and the dummy are both mentioned. It is not a simile. There is no figure of speech denoted by "like" or "as" that compares the human to the dummy. This is an analogy of two things through a literal statement.
For further illustration, we could change it to a metaphor like this: "the human one is watching is some kind of dummy." We could change it to a simile like this: "one is watching a human who is like some kind of dummy."