合同基于双方意思表示一致成立。双方意思表示一致包括双方意思表示的主观一致和客观一致，客观一致指意思表示的内容在客观上一致。合同的必要之点是合同成立所必须达成一致的因素，但合同必要之点并非合同成立要件。必要之点强调的是就此达成合意，而不是规定合意必须包含哪些内容，必要之点强调的是意思表示一致而不是必要。必要之点概念只是使得判定合意以及合同是否存在变得更加便利，区分必要之点与非必要之点的意义在于法律和法院可以简化合同成立裁决的标准和程序，以使更多的交易达成，法律规定必要之点在于促进交易。但交易内容纷繁复杂，包罗万象，法律几乎不能也不应该列举规定必要之点。理论和立法例都表明，必要之点强调的是关于它们的意思一致合同成立，不是着重讨论不合意。

The contract is based on the agreement of the parties. The agreement of intention expression of both parties includes the subjective agreement and the objective agreement. The objective agreement means that the content of intention expression is objectively consistent. The necessary point of a contract is the factor that must be agreed upon for the establishment of a contract, but the necessary point of a contract is not the essential element for the establishment of a contract. The point of necessity emphasizes to reach an agreement on this issue, not to stipulate what content the agreement must contain. The point of necessity emphasizes to express agreement rather than necessity. The concept of necessary point only makes it more convenient to determine the agreement and the existence of the contract. The significance of distinguishing the necessary point and the unnecessary point lies in that the law and the court can simplify the standards and procedures of the contract establishment decision, to make more transactions come to an end. The necessary point of the law is to promote transactions. But the contents of the transaction are complex and all inclusive, and the law can hardly and should not list the necessary points. Both theory and legislative examples show that the necessary point is to emphasize the establishment of a contract with the same meaning, not to focus on discussing the disagreements.