在科技写作中，我们常常要通过逻辑推理来对一个论点进行论证。常用的推理方法有两种：归纳推理和演绎推理。归纳推理是由个别到一般的推理，是由特殊事例推导出一般原理的思维方法。演绎推理是从一般到个别的推理，其前提通常是一般原理。

推理常用的表达：

...might result in...

...to conclude that...

If...then...

Accordingly，...

Thus.../therefore...

As a consequence...

This may imply that...

If...（Consequently）would...

The implications for...are...

Plainly/obviously/apparently/etc....

From the results，it can be seen that...

Research and observation reveal/show...

This study（result）indicated（suggested）...

Thus/Therefore/Consequently/In consequence/As a result...

1.归纳推理

归纳推理是从个别事物出发，收集例证，然后归纳出一般的道理来。由于它的前提常涉及个别事物，因而直接与经验有关。

例1：(www.daowen.com)

Mark Twain once projected with tongue-in-cheek that since the Mississippi River had been shortened by folds by 150 miles between Cairo，Illinois，and New Orleans during the 18th century，it was safe to conclude that the Mississippi would continue to shrink 1.5 miles per year indefinitely.Therefore，in 800 years Cairo，Illinois，and New Orleans，Louisiana，would become a single municipality，with a single city council and a common utility company.All this show what a heartening yield in speculation can be extracted from a trifling amount of information.

上段中用于证明结论的事实本身就是一个归纳推理的事例：马克·吐温从密西西比河变短这一事实进行推论，得出800年内开罗等城市将变成一个统一的大都市这一结论。作者由此事例推断出：一个微小的信息引发的思索，可能得出一个令人振奋的结论。

有时作者也可以先提出一个设想，然后再举出事例通过归纳法证明该设想的正确性。下例运用的就是这种方法。

例2：

Science and technology have contributed in several ways to the improvements of agricultural production.Scientifically compounded fertilizers make the land more productive.Chemical insecticides and pesticides，applied periodically to growing crops，selectively destroy a wide range of detrimental insects and pests.The numerous herbicides now available eliminate unwanted grasses and weeds，freeing crops for more abundant growth.Research in plant science has created hybrids which provide higheryielding plant strains and seeds.Moreover，technology has developed various kinds of machines such as tractors and combines which perform many timeconsuming tasks that once required a great deal of manual labour.Plainly，large-scale agricultural production depends heavily on developments in science and technology.

2.演绎推理

演绎推理是从一般到个别的推理，它来自形式逻辑的三段论法：大前提→小前提→结论。在推理时，先提出一般的论断作为大前提，再引用人所共知的事实作为小前提，进而推出结论。

以下就是一个典型的三段论的例子：

A.All human beings will die.

B.X is a human being.

C.Therefore，X will die.

例1.

Mathematics must deal with well-defined situations.Thus，mathematicians depend on an intellectual effort outside of mathematics for the crucial specification of the approximation that mathematics is to take literally.Give mathematicians a situation that is the least bit ill-defined，and they will make it well-defined，perhaps appropriately，but perhaps inappropriately.

在科技论文中，推理的表达形式是灵活多样的，表示推断关系的词语常常会被省略，这时，就需要从语义的联系上去分析前提和结论的推理关系。请看下段：

例2：

It has long been known that the rate of oxidative metabolism（the process that uses oxygen to convert food into energy）in any animal has a profound effect on its living patterns.The high metabolic rate of small animals，gives them sustained power and activity per unit of weight，but at the cost of requiring constant consumption of food and water.Very large animals，with their relatively low metabolic rates，can survive well on a sporadic food supply，but can generate little metabolic energy per gram of body weight.

本段的大前提是：所有动物氧化新陈代谢的速度都会对其生存方式有重大影响。小前提是：小动物和大动物都是动物。结论是：小型动物的高新陈代谢速度使得它们必须不断消耗食物和水；而大型动物的新陈代谢速度相对较慢，在食物供给零星不定的情况下也能生存得很好。