From the whitepaper; "If a greedy attacker is able to assemble more CPU power than all the honest nodes, he would have to choose between using it to defraud people by stealing back his payments or using it to generate new coins. He ought to find it more profitable to play by the rules, such rules that favour him with more new coins than everyone else combined, than to undermine the system and the validity of his own wealth."
This assumes a purely economic model - what if there is a bad actor that is motivated more by political power that has vast resources to throw at the problem?
From the whitepaper; "If a greedy attacker is able to assemble more CPU power than all the honest nodes, he would have to choose between using it to defraud people by stealing back his payments or using it to generate new coins. He ought to find it more profitable to play by the rules, such rules that favour him with more new coins than everyone else combined, than to undermine the system and the validity of his own wealth."
This assumes a purely economic model - what if there is a bad actor that is motivated more by political power that has vast resources to throw at the problem?