A “basic presumption” is an assumption that deals with an essential fact of the agreement. Wrong beliefs must have such a strong influence on trade that the imbalance is such that it would be unfair to apply the treaty.  For example, at Renner v. Kehl, two vendors decided to sell leases on 2,000 hectares of undated land near Yuma, Arizona. The sellers were approached by a buyer who wanted to rent the land for the cultivation of Jojoba (ha-ho`ba), a shrub whose seeds produce precious oil, in the countryside. The country seemed perfect for commercial production of jojoba. Both sides believed that there was enough water under the country that could maintain commercial production of jojoba. After the contract was signed, the parties found that there was not enough water to maintain these agricultural activities and the buyer therefore wanted to cancel the contract. The contract was cancelled because both parties in principle concluded that there was sufficient water to maintain production.
The acceptance had a significant effect on the contract, as the parties entered into the contract only on the assumption that the purchaser could cultivate Jojoba on the land.  A contract may be “unacceptable” if the values exchanged are largely disproportionate.  Whether the terms are unacceptable is determined on a case-by-case basis. For example, when a contractor files an offer that is $50,000 less than it would normally have been because the contractor has miscalculated, a court may consider that unacceptable, making the agreement unenforceable. However, if the offer is only $5,000 less than usual, that may not be unacceptable.  If the parties have given different meanings to one term, but one party is not aware of the adoption of the other party, it will be bound by the acceptance of that other party.  For example, a buyer and a seller enter into a chicken exchange agreement. The buyer thinks there is only one type of chicken called broiling chickens.
The seller knows that there are two types of chickens, thirsty chickens and broiling chickens, and he knows that the buyer wants broiling chickens. In this case, the seller would have to provide the buyer with broiling chickens, even if the seller really intended to offer tangy chickens. “error” can be a defence against the application of a contract if at least one party had a “belief that does not correspond to the facts” with respect to the important terms of the contract.  The error relates to the false convictions of the parties that led them to enter into agreements, not to errors relevant to the actual implementation process of the agreement. For example, this defence is not relevant to the scenario that a party signed an agreement because it thought it was signing a credit card receipt; However, such an agreement could not be applicable, even in the absence of valid approval. By allowing this defence of errors, misunderstandings and misrepresentations, contract law is intended to protect the parties from agreements that have never linked them. These are consistent with the general objectives of contract law, which are to protect the reasonable expectations of sensible people. One of the limitations of this rule is that the party concerned can only avoid the contract if it has not taken the risk of making the error. On the other hand, if it is the nature of the agreement that a party takes a risk, the appearance of the expected danger does not constitute a “mistake” and does not avoid the contract. For example, if a land buyer knows that title insurance does not issue title insurance because it suspects some kind of title error, the subsequent discovery of a default is not a defence of error.