Try jotting it down and then reasoning it out as an individual in the tribe.
(1) Suppose there are 4 browns, b1 to b4, and b1 is trying to figure out if his eyes might not be brown.
(2) b1 wants to know if it's logically possible for his eyes not to be brown and for the others not to know their eye colour.
(3) b1 therefore supposes b1 has green eyes. If this were the case, b2 would see b1's green eyes and both b3 and b4 having brown eyes.
(4) If then b2 imagined b2 had green eyes, b3 would see b1 and b2's green eyes, and b4's brown eyes.
(5) If then b3 imagined b3 had green eyes, b4 would see three sets of green eyes.
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(6) So b1 can imagine a situation, where b2 imagines a situation, where b3 imagines a situation, where b4 sees three sets of green eyes.
(7) If everybody on the island knew at least one person had brown eyes then in b1's imaginary scenario, b4 would know they had brown eyes and would commit suicide on day 1.
(8) If this didn't happen then we'd know that at least 2 people had brown eyes by day 2, and the induction takes off.
Since they don't know that at least one person has brown eyes, then b1's imaginary scenario is possible, and it's therefore possible that b1 doesn't have brown eyes.
Try jotting it down and then reasoning it out as an individual in the tribe.
(1) Suppose there are 4 browns, b1 to b4, and b1 is trying to figure out if his eyes might not be brown.
(2) b1 wants to know if it's logically possible for his eyes not to be brown and for the others not to know their eye colour.
(3) b1 therefore supposes b1 has green eyes. If this were the case, b2 would see b1's green eyes and both b3 and b4 having brown eyes.
(4) If then b2 imagined b2 had green eyes, b3 would see b1 and b2's green eyes, and b4's brown eyes.
(5) If then b3 imagined b3 had green eyes, b4 would see three sets of green eyes.
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(6) So b1 can imagine a situation, where b2 imagines a situation, where b3 imagines a situation, where b4 sees three sets of green eyes.
(7) If everybody on the island knew at least one person had brown eyes then in b1's imaginary scenario, b4 would know they had brown eyes and would commit suicide on day 1.
(8) If this didn't happen then we'd know that at least 2 people had brown eyes by day 2, and the induction takes off.
Since they don't know that at least one person has brown eyes, then b1's imaginary scenario is possible, and it's therefore possible that b1 doesn't have brown eyes.