Man, I agree with you. This kind of reasoning is bizarre, how could you possibly know the strategies of the other players? And yet it&#x27;s right. Read the first sentence of <a href="https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Nash_equilibrium" rel="nofollow">https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Nash_equilibrium</a>, which is brilliant in its simplicity:<p>&gt; <i>In game theory, the Nash equilibrium is a solution concept of a non-cooperative game involving two or more players, in which each player is assumed to know the equilibrium strategies of the other players, and no player has anything to gain by changing only their own strategy.</i><p>Many people have tried to define mathematically what &quot;rational behavior&quot; means when there are multiple players. Nash equilibrium is the one idea that stayed. It&#x27;s the first chapter of every game theory textbook. Since the 1950s, literally all publications about non-cooperative games have been based on Nash equilibrium. To understand why, you&#x27;d have to look at the history of the field, or you could take my word for it. If it&#x27;s any consolation, it was very unintuitive for me at first, too.