Because conditions will change after parties enter into a contract, there are tremendous advantages to maintaining flexibility to adjust the arrangement in the light of changed circumstances. There will also, however, be opportunities for one party to take advantage of the other's isolation from market alternatives and insist that an existing contract be modified in its favor. Contract law faces the difficult task of facilitating the former while attempting to restrict the latter. The common law utilized the preexisting duty concept to police attempts to modify contracts while the Code has utilized the notion of good faith modification.

The four selections in Part VIII are all concerned with this problem. It should be clear to the reader that the problem is another variation on the Boomer problem. The party requesting the modification is in the same position as the party that might get the injunction. The more it appears that this party is simply taking advantage of the other's vulnerability, the more likely it is that the court will intervene (providing only damages in the case of the cement company and invoking some variant of the preexisting duty doctrine in the contract case). On the other hand, the more the opposite party was responsible for its own plight, the less willing a court will be to bail it out. One can perhaps read Hackley et al. v. Headley (discussed by Dalzell [8.1]) as holding that if a party is vulnerable to a request to modify because it is on the verge of bankruptcy, this condition is entirely of its own making; its “fault” makes it extremely unlikely that the opposite party's behavior would be found unlawful.