自布伦塔诺在现代哲学中引入“意向性”作为心理区别于物理的独特标志以来，如何理解这种性质成为人们非常感兴趣的话题。意向性属于民间心理学意义上的概念，对它的理解具有重要意义，其相对于未来科学心理学的地位应该得到辩护，否则我们的选择就只有二元论和取消主义了。而且，为了与遵循严格因果律的物理世界相一致，我们也面临一个如何把意向性镶嵌到物质世界中的问题。在最近几十年，将意向性自然化成为当今心灵哲学中的主流趋势。这种自然主义主张：我们对心灵、知识和语言的解释必须最终是与自然科学一致的、和谐的。意向性是心理状态的重要属性之一，但并非所有心理状态都有意向内容，依据命题内容、经验所具有的不同维度，心理现象可以分为具有不同性质和内容的两类：命题态度和感觉质状态。而对意向性的自然化就是通过对命题态度的自然化而进行的，命题态度像意向内容、思维内容一样都是语义的载体，因而具有意义、指称和真值条件，能够反映意向性的特征。对意向内容的性质有两种看法或争论，即关系属性、非关系属性，以密立根等人为代表，对意向内容持关系属性观点，因而赞成外在论立场；而福多等人对之则持非关系属性观点，因而赞成内在论立场。 在密立根之前，就有众多对意向性自然化的路径，其中德雷斯基的因果的信息理论影响最为巨大，但是他的这一理论因为功能的不确定所导致的析取难题而无法完成意向内容自然化的任务。之后，福多提出了非对称依赖性理论来试图解决这一难题，但因为析取难题内在于意义的因果解释中，因果层面并非意向性自然化的合适层面。密立根不同意布伦塔诺关于意向性的看法，因此提出了基于原因论的生物专有功能理论的“生物目的论”理论继续探讨这个问题。她通过专有功能把自然目的转化为意向目的，进而对公共语言的意向性、表征内容和人类的高级意向性（语言和思维）提出了自然化解释的方案。其中，对公共语言意向性的自然化解释包括稳定化的专有功能、弗雷格含义和内涵三个方面，但是意义产生的关键，就在于由表征的制造者、表征和消费者构成的表征系统中，制造者和消费者相互合作，通过消费者专有功能的行使，使其依据特定的对应规则而与世界相一致，这种说明方式也适用于人类的思维和语言。然而，虽然密立根的生物目的论具有解释上的简单性、统一性，但是由于其对生物进化论的过度依赖，她所强调的对错误表征问题的“为什么被选择”的解释仍然是不充分的，因而受到福多等人的反驳。除此之外，也还有其它关于生物目的论的责难，密立根也提出了相应的回应。但不管怎样，密立根还是坚持其强的外在论立场，而且通过强调自己所谓的“新实在论”的合理性，对“所与神话”的残余——意义理性主义进行了彻底批评。总之，关于意向内容自然化的工作在哲学史上只有最近几十年的较短历史，生物目的论也同样如此，它有不足和缺陷是在所难免的，需要在以后继续修改和完善。

Since Brentano introduced "intentionality" into the modern philosophy as a distinct symbol between the mental and the physical, how to understand the property becomes a very interesting topic among people. The concept of intentionality is a folk psychology concept, it is important to understand it and its status which relative to the future scientific psychology should get proper defense, otherwise our only choose are dualism and eliminativism. Besides, in order to correspond to the physical world that complies with strict causal laws, we also face a problem of how to embed the mind into the material world. In recent decades, making intentionality naturalized becomes a main trend in philosophy of mind. The naturalism maintains that our interpretation of the mind, knowledge and language must ultimately be consistent and harmony with natural science. Intentionality is one of psychological state’s important features, but not all of the mental states have intentional content, based on different dimensions of propositional contents and experiences have, the mental phenomena can be divided into two groups that with different properties and content: propositional attitudes and qualitative states. The same as intentional contents and thought content, propositional attitudes is also the carrier of semantics, thus all of them has a meaning, reference and truth conditions, which can reflect the characteristics of intentionality, so the naturalization of intentionality proceeds in terms of the naturalization of propositional attitudes. There are two views or disputes that concern the nature of intentional content’s property, namely relational or non-relational. In virtue of Millikan and other people insist that intentional content is relational, they thus in favor of the externalism position; but Fodor and others support the non-relational view, and therefor they favor internal position. Before Millikan, there are many paths to naturalizing intentionality, among which Dretske’s causal information theory have the greatest influence, but because of the disjunction problem caused by function indeterminacy, his theory cannot complete the task of naturalizing intentional content. After that, Fodor proposed an asymmetric dependence theory, which attempts to solve the difficulty, but as the disjunction problem is internal to the causal interpretation of meaning, the causal level is not appropriate for naturalizing intentionality. Millikan doesn’t agree with Brentano's views on intentionality, thus she proposed the theory of "biological teleology" which based on the etiology theory of biological proper functions to continue discussing the issue. Her strategy is to transform natural purpose into intentional purpose through proper functions, and thus suggests naturalizing explanation scheme for the intentionality of public language, representational content and human’s high-level intentionality （language and thought）.To be specific, the explanation of naturalizing public language’s intentionality includes three parts :stabilizing proper function, Fregean sense and intension , but the key to generate meaning lies in the representational system which composed of representation producer, representation and consumer, the producer and consumer cooperates with each other, then through consumer performs its proper function by specific mapping rules to correspond to the world, this explanation mode also fit to explicate human’s thought and language. However, although Millikan’s biological teleology has the virtue of simplicity and unity in explanation, but because of its excessive dependence on biological evolution, she emphasizes the "selected for" interpretation for misrepresentation problem is still not sufficient, thus get rebuttal from Fodor et al. In addition, there are also other accusations on biological teleology and Millikan gives the corresponding response. But at any rate，Millikan still maintains her strong externalism position and delivers the remains of "Myth of the Given" , namely meaning rationalism, a thorough criticism，by laying stress on her own so-called validity of “new realism” .In sum, the work on naturalizing intentional content in the history of philosophy is only recent decades, biological teleology is also the same case, it is inevitable to have shortcomings and deficiencies, which needs to continue to modification and improvement in the future.