论说文是书面语体中运用得非常广泛的一种文体，通常分为议论和论述两种，是相对于散文中的记叙（Narration）和描写（Description）而言的。其常见形式包括社科论著、论文、评论、演讲、讲座、报告等。论说文的文体特点主要有以下几条：

　　1） 措词严谨规范。论说文的功用主要在于对某一观点进行解释、说明或阐述，因此，此类文章讲求理性与逻辑性，在措词上表现为正式语体的词、大词、抽象词、外来词用得较多，而绝少使用俚语俗语及过于口语化的词，以体现其庄重、严谨的特点。

　　2） 句法及篇章结构较为复杂。由于论述文旨在解析思想，阐发论点，辨明事理，展开论证，因此文章内容往往比较复杂。为全面、慎密地表述自己的见解，避免片面、疏漏，论说文中往往长句、复杂句使用较多。另外论说文讲究谋篇布局及条理层次，因而在篇章结构上较为复杂，往往段落之间环环相扣，层层递进。除此之外，论说文还十分讲究修辞，辞格上多用排比、递进、设问等，以增强文章的感染力和说服力。

　　下面一例节选自一篇论说文，它较为清晰地显示了论说文体的主要特点：

Science and Ethics?

　　Science impinges upon ethics in at least five different ways.

　　In the first place, by its application it creates new ethical situations. Two hundred years ago the news of a famine in China created no duty for Englishmen. They could take no possible action against it. Today the telegraph and the steam engine have made such action possible, and it becomes an ethical problem what action, if any, is right. Two hundred years ago a workman generally owned his own tools. Now his tool may be a crane or steam hammer, and we all have our own views as to whether these should belong to shareholders, the State, or guilds representing the workers.

　　Secondly, it may create new duties by pointing out previously unexpected consequences of our actions. We are all greed that we should not run the risk of spreading typhoid by polluting the public water supply. We are probably divided as to the duty of vaccinating our children, and we may not all be of one mind as to whether a person likely to transmit club foot or cataract to half his or her children should be compelled to abstain from parenthood.

　　Thirdly, science affects our whole ethical outlook by influencing our views as to the nature of the world-in fact, by supplanting mythology. One man may see men and animals as a great brotherhood of common ancestry and thus feel an enlargement of his obligations. Another will regard even the noblest aspects of human nature as products of a ruthless struggle for existence and thus justify a refusal to assist the weak and suffering. A third, impressed with the vanity of human efforts amid the vast indifference of the universe, will take refuge in a modified epicureanism. In all these attitudes and in many others there is at least some element of rightness.

　　Fourthly, in so far as anthropology is becoming scientific, it is bound to have a profound effect on ethics by showing that any given ethical code is only one of a number practiced with equal conviction and almost equal success; in fact, by creating comparative ethics. But, of course, any serious study of the habits of foreigners, whether scientific or not, had this effect, as comes out plainly enough in the history of ancient Greek ethics. Hence science is not wholly responsible for the ethical results of anthropology.??