Why, in An Inspector Calls, can inspector Goole be perceived as unreal and what is the meaning of this?

Inspector Goole is the concretization of our conscience. He symbolizes our guilt and aspects relating to the acceptance of such guilt. Priestly uses the inspector to personify mankind's responsibility for the destiny of others. It is for this reason that he is not real.

Moreover, the inspector's demeanor throughout the play, as well as Priestly's initial depiction of him, speaks of an individual who reflects a supernatural essence. When the inspector enters the scene, he is described in the following terms:

The inspector need not be a big man but he creates at once an impression of massiveness, solidity and purposefulness. He is a man in his fifties, dressed in a plain darkish suit of the period. He speaks carefully, weightily, and has a disconcerting habit of looking hard at the person he addresses before actually speaking.

The description suggests that the inspector projects an innate power. His aura reflects someone of stature, an important individual. The manner of his speech also conveys a unique authority and a focus on what is important. Furthermore, his 'disconcerting habit of looking hard at the person he addresses before speaking' emphasizes this natural authority. His audience is instinctively ill at ease when he addresses them. Individually, they feel vulnerable when he addresses each of them.

The inspector's manner further conveys his authority. He is direct and to the point. He has no time for trivial chatter and deals with each of his targets in an even manner. He treats all of them equally and shows no sympathy for their point of view. He is remarkably unaffected by their responses on an emotional level and sticks to the facts. He is brutally honest.

More remarkable is the meticulous and merilessly direct manner in which he speaks about Eva's death. Whenever he mentions her, there is no hint of sentiment whatsoever. He, for example, tells his listeners in Act 1:

Two hours ago a young woman died on the infirmary. She'd been taken there this afternoon because she'd swallowed a lot of strong disinfectant. Burnt her inside out, of course.

His report is cold and clinical. Even Eric's shocked response leaves him unaffected and he continues in a very matter-of-fact manner:

Yes, she was in great agony. They did everything they could for her at the infirmary, but she died. Suicide, of course.

Clearly, inspector Goole's demeanor is not what one would expect from someone human - it is too extraordinarily unaffected. His audience, however, goes through a range of emotions throughout the play. 

Another indicator that the inspector cannot be human is the fact that he knows everything about everyone in the room's relationship with Eva, and this after learning about her death only a short time before. The best team of detectives in the world would not possibly have learned so much about a victim in such a short period of time. It would have taken months of investigation to gather so much evidence. The inspector seems to possess an a priori knowledge of Eva and his listeners - a definite indication of a supernatural power.

Finally, definite proof of the inspector's supernatural identity is found in the final lines of the play:

Birling: That was the police. A girl has just died – on her way to the Infirmary – after swallowing some disinfectant. And a police inspector is on his way here – to ask some – questions.

After inspector Gool had left, the family surmised about the fact that he was a fraud. Gerald had discovered that he was not stationed at the local constabulary and, in the end, he and the senior Birlings were quite relieved about having discovered the truth. Only Sheila and Eric were truly remorseful.

Later, Mr. Birling received the above-mentioned call, which shocked everyone, for they realized that they had just experienced an encounter with the supernatural.

As already mentioned, inspector Goole epitomizes our conscience. More specifically, though, his purpose was to make the Birlings, as well as Gerald, aware of their responsibilities with regard to especially those of a lesser persuasion, when they deal with them. He was there to make them aware of how self-absorbed they had been and how they were dismissive of the needs of others, symbolized by Eva. They were to acknowledge their role in her unfortunate death instead of being indifferent. As he says, in the final act:

But just remember this. One Eva Smith has gone – but there are millions and millions and millions of Eva Smiths and John Smiths still left with us, with their lives, their hopes and fears, their suffering and chance of happiness, all intertwined with our lives, and what we think and say and do. We don't live alone. We are members of one body. We are responsible for each other. And I tell you that the time will soon come when, if men will not learn that lesson, then they will be taught it in fire and blood and anguish. Good night.