Please explain the conflict between the rational and the irrational in Lord of the Flies.
The conflict between the rational and irrational is most clearly presented in the conflict between the boys: it is Ralph and Piggy versus Jack and his tribe of savages. Ralph and Piggy are proponents of civilization and desperately attempt to establish a civil society on the uninhabited tropical island. Both Ralph and Piggy create rules regarding the conch, feel that it is important to maintain the signal fire, and try to organize the construction of huts on the beach. Ralph and Piggy demonstrate rational thought by attempting to put the group of boys in the best possible position to be rescued. Jack and his savages act as the antagonists and completely disregard the rules and established institutions on the island. They favor irrational thought and desire to survive on instinct by hunting and relaxing by the pool all day. During the boys' time spent on the tropical island, Golding illustrates mankind's inherent wickedness by depicting how Jack successfully usurps power and how the majority of boys descend into savagery. When Jack becomes the most powerful leader on the island, irrational thought reigns supreme, and violence erupts. The conch can symbolically represent democracy, civility, and rational thought. Once the conch is destroyed, any hope of establishing a rational, civil society on the island is lost.
If you want to look at rational and irrational, many people consider Ralph and Piggy to be the personification of rationality in the book, representing the ideas of society, rules, order, etc. Their main enemy is Jack as he tries to embrace chaos and the pursuit of almost hedonistic pleasure. He urges the boys to think only of their hunger, their desire to hunt, to take pleasure in the hunt and the kill.
For individual versus collective you might look closely at Simon. He is the only boy to realize where the real beast is and as he tries to share this knowledge with the group, they attack and kill him, fearing any individual intruder.