履行不能这一概念具有双重指向：一方面，它可以指向逻辑上的不可能，例如罗马法中的履行不能就是这个意义上的；另一方面，履行不能也可以指向债务人的能力或者更为规范性的评价，这种规范性的不能在历史与比较的视角下并不少见。《民法典》第580条第1款也是如此，该款第1项属于逻辑性的不能，第2、3项则属于规范性的不能。这一认识能够帮助我们更好地理解实证法中履行不能的含义，如516条第2款中的“不能履行”。在实际履行的问题上，存在三种模式可供选择：实际履行原则、金钱赔偿原则以及二者的折中模式。我国民法实行的是较为严格的实际履行原则，履行不能构成对其的重要限制。这种限制的正当性可以分两个角度观察：逻辑性不能的正当性可以归结为债务的本质及规范的无矛盾性所要求。规范性不能的正当性则可以归结为禁止权利滥用原则。具体而言，《民法典》第580条第1款第2项是基于比例原则而禁止权利滥用，第3项则是出于信赖保护而禁止权利滥用。逻辑性不能分为事实上与法律上不能，前者为自然法则意义上的不可能，后者则是因为法律性的原因而不能。在义务的消灭上，目的实现与目的落空按一般规则处理，但债务人的对待给付利益应特殊处理，所谓的“受领不能”亦同。金钱债务原则上不发生履行不能，其背后的思想是任何人均须对其支付能力负责。一时不能亦属履行不能，但需要特别规则处理，在构成上，除绝对定期行为外并不需要额外的判断标准，部分不能同理。履行费用过高是指履行费用相较于债权人实际履行利益而失衡，其适用分两步走：先确定哪些当事人利益纳入衡量，再考虑“过高”的标准与影响因素。债务标的不适于强制履行应限于强制实际履行不合理的人身性债务，又可类型化为两类：债务性质本身即反对强制实际履行与因为某种嗣后的障碍而不可期待债务人履行。这一规则可与强制执行法的“正当理由”除外规则发生联动。债权人在合理期限内未请求履行，存在被时效制度遮蔽的问题，应根据其规范目的重述。《民法典》第580条第2款进一步赋予了债务人主动消灭合同关系，使双方进入清算状态的权利。理解该款必须先理解何谓合同僵局。常见的合同僵局有两类，一类严格以出现前款的履行不能为前提，在此类僵局中债务人面临的困境往往存在于部分不能的场合，其破解可直接适用第580条第2款。第二类则出现在租赁等继续性合同中，且其与前款并无必然关联，但鉴于第580条第2款所承载的规范目的，可以目的论扩张该款的适用，将其运用于此类合同僵局的破解。

The concept of performance impossibility has a double point: on the one hand, it can point to logical impossibility, such as performance impossibility in the Roman law; on the other hand, it can also point to the debtor‘s capacity or a more normative evaluation, such normative impossibility is not uncommon in a historical and comparative perspective. This is also the case with article 580, paragraph 1 of the Civil Code, where the first subparagraph is logical impossibility and the second and third subparagraphs are normative impossibility. This understanding can help us better understand the meaning of performance impossibility in empirical law, such as the "performance impossibility" in article 516, paragraph 2.There are three models to choose from when it comes to specific performance: the principle of actual performance, the principle of monetary compensation, and a compromise between the two. Our civil law applies the principle of specific performance in relatively strict sense, and performance impossibility constitutes an important restriction on it. The legitimacy of this restriction can be seen from two perspectives: the legitimacy of logical impossibility can be attributed to the nature of the debt and the non-contradictory nature of the norm, while the legitimacy of normative impossibility can be attributed to the principle of prohibition of abuse of rights. Specifically, article 580, paragraph 1, subparagraph 2 of the Civil Code prohibits abuse of rights based on the principle of proportionality, while subparagraph 3 prohibits abuse of rights due to reliance protection.Logical impossibility is divided into factual and legal impossibility, the former is impossibility in the sense of natural law, and the latter is impossibility for legal reasons. As to the extinguishment of the obligation, realization of purpose and frustration of purpose (目的实现与目的落空) should be treated according to the general rules, but the debtor‘s interest in counterperformance should be treated in a special way, as well as the so-called "impossibility to accept". The monetary obligation will not be impossibly usually, the idea behind this rule is that any person is responsible for his or her ability to pay. Temporal impossibility is also impossibility, but it requires special rules, and in terms of definition, no additional criteria are required other than in the case of acts with absolutely fixed period (绝对定期行为), and the same applies to partial impossibility.Excessive cost of performance means that the cost of performance is out of balance with respect to the creditor‘s interest in specific performance, and is applied in a two-step process: first determine which interests of parties are to be included in the measurement, and then consider the criteria for determining whether it is "excessive" and the factors affecting this determination. The unsuitability of the subject matter of the debt for compulsory performance should be limited to personal debts where compulsory performance is unreasonable, and can be typified into two categories: those where the nature of the debt itself is against compulsory performance, and those where the debtor cannot be expected to perform because of some subsequent impediment. This rule can be linked to the "good cause" exclusion rule of the enforcement law. The creditor‘s failure to request performance within a reasonable period of time is obscured by the statute of limitations and should be restated in accordance with its normative purpose.Article 580, paragraph 2 of the Civil Code further grants the debtor the right to extinguish the contractual relationship and put the parties into liquidation. To understand this paragraph, one must first understand what is meant by a contractual impasse. There are two common types of contractual impasses, one strictly presupposes performance impossibility in the sense of the preceding paragraph, and in such impasses the predicament faced by the debtor often exists in the case of partial impossibility, and to its crack article 580, paragraph 2 can be directly applied. The second category is found in continuing contracts such as leases, which are not necessarily related to the preceding paragraph, but in view of the normative purpose carried by article 580 paragraph 2, the application of this paragraph can be expanded purposefully and applied to the resolution of such contractual impasse.