Asimov made up positronic brains, but in these stories, there are scientists who understand those brains. For instance, in the Introduction, Calvin is described as being able to figure out how positronic brains work. But no one knows how a "positronic field" works. How do you react when you read that? On one hand, it seems like a reminder that science moves forward; on the other hand, it seems like a bit of foreshadowing for "The Evitable Conflict," when the Machines are too complex for the humans to check.