| Quote #4
"All around us are people, of all classes, of all nationalities, of all ages. For three days these people, these strangers to one another are brought together. They sleep and eat under one roof, they cannot get away from each other. At the end of three days they part, they go their several ways, never, perhaps, to see each other again." (1.3.7)
The train brings together people of all classes and nationalities, creating a melting pot sorts. In this way, "modern" technology brings people together.
| Quote #5
"No fingerprints at all," he said. "That means it has been wiped. Well, if there had been fingerprints it would have told us very little. They would have been those of M. Ratchett or his valet or the conductor. Criminals do not make mistakes of that kind nowadays." (1.7.13)
Fingerprint technology exists, but Poirot doesn't think it would help. He knows he must rely on the age-old tools of logic, reason, and psychology.
| Quote #6
"See you, my dear doctor, me, I am not one to rely upon the expert procedure. It is the psychology I seek, not the fingerprint or the cigarette ash. But in this case I would welcome a little scientific assistance. This compartment is full of clues, but can I be sure that those clues are really what they seem to be?" (1.7.112)
Poirot is not immune to scientific intervention. He relies on the Doctor's medical examination for evidence, and also uses a spirit stove and hat mesh to reveal the writing on a discarded scrap of paper.