合同法合同的成立要件:通过要约和承诺达成合意(Agreement)当事人具有缔约能力(thelegalcapacitytocontract)存在对价(Consideration)或对价(Cause)合同形式符合法律规定具备合法性合意必须真实(Intentionofparties)要约(Offer)要约人offerer受要约人offeree邀请邀约invitationforoffer要约的确定性definiteness要约人受约束的意旨intentiontobebound特定人specificpersons要约的撤回withdrawalofoffer要约的撤销revocationofoffer确定的要约firmoffer要约的消灭/终止termination承诺Acceptance镜像规则mirrorimagerule反要约counteroffer承诺生效的时间英美法:邮箱规则:mailboxrule(发出时有效,有利于受要约人,缩短要约人可撤销要约的时间)大陆法:德国、合同通则:到达生效原则receiptrule合同的效力Validity有效合同legal无效合同void可撤销合同avoidable效力待定/不可强制执行的合同影响合同效力的因素:错误mistake:重大误解substantialmisunderstanding欺诈fraud胁迫duress显失公平不正当影响undueinfluence不履行(non-performance)可免责的不履行excusednon-performance不可抗力forcemajeure/impedimentbeyondcontrol:无法控制;无法预见;无法避免;无法克服重大违约materialbreach轻微违约minorbreach预期违约anticipatorybreachofcontract违约的救济方式rem