The first thing you might notice about the explorer is that, well, there's not a whole lot to notice about him. While we get colorful descriptions of the other characters – the condemned man is described as a "submissive dog" (1), the heavily uniformed officer is "uncommonly limp" and "breathe[s] with his mouth open," (2) – we hear nothing about how the explorer looks. We don't get any background on him, or any description of strong emotions going on inside of him. The only thing we do hear about is that he's kind of bored and distracted by shiny things (namely the sun):
The explorer did not care much about the apparatus and walked up and down behind the prisoner with almost visible indifference. (2)
He had not been listening very attentively, the glare of the sun in the shadeless valley was altogether too strong, it was difficult to collect one's thoughts. (3)
It doesn't seem like there's that much to the explorer. The explorer is not a spectacle. He's just the pair of eyes in the story (see "Narrator Point of View"), who watches the real spectacle unfold. Most of the story is just the officer talking – about the machine, the procedure, the lovable old Commandant – and the explorer listening or watching. In that way, the explorer is a stand-in for the reader within the story, since the reader is also just "observing" the strange world of the penal colony.
The one significant thing we learn about the explorer is that he's "a famous Western investigator, sent out to study criminal procedure in all the countries of the world" (25). So what is it he does for a living? He observes. Maybe that's why he's bored and tired. By the time he's visited the penal colony, he probably thinks he's seen it all, and would rather not be stuck in some tropical armpit of a penal colony with bright sun and sweltering heat.
Of course, the explorer doesn't just watch; he also has reactions. You can actually look at the whole story as the escalation or intensification of the explorer's reaction to what he's seeing, as he gets more drawn in to (and troubled by) what he sees. What's striking is how gradually it happens. It begins when, after that opening stint of boredom, he feels a "dawning interest" (4). Even after learning that the condemned man has had no trial, is being sentenced to death for disobedience, and will have his sentence "written on his body," the explorer is still only mildly dissatisfied!
The explorer considered the Harrow with a frown. The explanation of the judicial procedure had not satisfied him. (14)
After he hears about how the agonizing twelve hours of lethal torture will unfold for the condemned man, the explorer thinks to himself, "It's always a ticklish matter to intervene decisively in other people's affairs" (19). We would have totally lost it by then. It's absurd how understated his reactions are to such a gruesome procedure.
The explorer seems to think of everything in abstract or intellectual terms. It's a matter of principles. He's made the principle of "non-intervention" an operating procedure for him by now: "He traveled only as an observer, with no intention at all of altering other people's methods of administering justice" (19). And his disapproval of what's going on in the penal colony is made from principle, from his commitments to general ideas of justice and humaneness: "the injustice of the procedure and the inhumanity of the execution were undeniable" (19).
The explorer's principles are pretty easy to identify with – they're presumably the reader's, which is another way he's like a stand-in for the reader. But it's worth noticing that, as far as actual sympathy for the condemned man goes, it's basically nil:
No on could suppose that he had any selfish interest in the matter, for the condemned man was a complete stranger, not a fellow countryman or even at all sympathetic to him. (19)The explorer represents a certain hollowness that Kafka seems to find contemptible, and can be seen as characteristically "modern." The explorer "tolerates" people and believes in their rights as a matter of principle without feeling sympathy for them. He believes in the "rightness" of one's convictions without really feeling them, unlike the officer.
The explorer is very removed and rather without feeling, unlike the officer (see the officer's "Character Analysis"). In fact one of the only strong reactions we get from the explorer (until the end) is when the officer, in a fit of excitement, embraces the explorer and puts his head on his shoulder. The explorer is "deeply embarrassed" and stares "impatiently […] over the officer's head" (22). Painful executions don't seem to ruffle him (he's probably seen a lot of those, anyway), but having another man get all emotional with him makes him uncomfortable.
However, the explorer admires the officer for the force and passion of his belief. But even this admiration feels removed. The explorer doesn't seem to care about what the officer believes – by his standards, it's pretty horrific – but thinks it nice that the officer is so committed. He's "touched" by the officer's "severe conviction" (30).
It takes the machine going haywire and the officer getting gorily slaughtered to get a real reaction out of the explorer. Not that the explorer goes hysterical or anything. He keeps his composure. But when we're told simply that the explorer feels "greatly troubled" (46) watching the officer, he rather helplessly reaches out a hand, and that ultimately he's forced to look into the officer's face "almost against his will." We think this indicates some pretty deep inner turbulence (of the psychic, not the gastric variety).
We as readers feel more uneasy being told that he's "greatly troubled" than we would if all the details of his being "troubled" were spelled out. It leaves more room for the imagination, and in a nightmare world like that of "In the Penal Colony," that's scary.
The explorer really must be "deeply troubled" because he leaves the penal colony so soon after the officer is killed, and "wards off" the soldier and the condemned man – as if to make sure nothing of the place comes with him. This gives his departure the feeling of an escape. Having seen what he saw, he now needs to get away from the penal colony. Kind of like Marlow in Heart of Darkness: "The horror…the horror!"
So the explorer has been startled out of his earlier state by the end of the story. Here again he's just like a frame for the reader, who by the end of the story is also quite disturbed and ready to get the heck out of "In the Penal Colony." The explorer thought he'd seen it all, but he hadn't.
But exactly what has the explorer seen that troubles him so? Hearing about how gruesome the execution procedure was hadn't made him "greatly troubled." It's a good question, and a hard one to answer. So go check out "What's Up with the Ending?" and start taking a crack at it.