The author’s purpose is to remind people that small actions have large consequences.
The author’s purpose is the reason for writing a story. Usually we first determine if an author intends to inform, persuade or entertain. The short story “A Sound of Thunder” by Ray Bradbury is a cautionary tale. It is entertaining, because most science fiction is. But its primary purpose is to get us to think.
Since people cannot really travel through time, we cannot say that Bradbury is cautioning us with interfering with the past. Through the message of the “butterfly effect,” Bradbury lets us know that apparently small actions can have huge consequences.
Eckels felt himself fall into a chair. He fumbled crazily at the thick slime on his boots. He held up a clod of dirt, trembling, "No, it can't be. Not a little thing like that. No!"
Bradbury wants us to consider: If stepping on a butterfly in the past can cause the entire future to be altered, what other small actions might we make that have unintended, large effects?