3、You have all heard it repeated that men of science work by means of induction (归纳法）and deduction, that by the help of these operations, they, in a sort of sense, manage to extract from Nature certain natural laws, and that out of these, by some special skill of their own, they build up their theories.

【分析】

复合句。句子主干为You have all heard it repeated that…，that…，and that… ，it为形式宾语，真正的宾语是三个并列的that从句。第一个从句中，by means of induction and deduction为方式状语，翻译时，应置于谓语动调之前。第二个从句的主干为they…manage to?extract…certain natural laws，状语 in a sort of sense 可译于从句句首，状语by the help of these operations译于主谓之间，from Nature译于动词extract之前。第三个从句采取顺译法，they指代上一句的certain natural laws，需明确。

【点拨】

1、extract from “从…中提取”。2、 build up“逐步建立；增进，增强；积累”。

【译文】

我们都多次听说过，科学家是用归纳法和演绎法工作的，而且从某种意义上说来，他们依靠这种方法力求从自然界归纳某些自然规律，然后根据这些规律和自己的某种非同一般的本领，建立起他们的理论。

4、And it is imagined by many that the operations of the common mind can be by no means compared with these processes, and that they have to be acquired by a sort of special training.

【分析】

复合句。句子主干为it is imagined that…and that…，it为形式主语，真正的主语是两个并列的that 从句。主句为被动语态，翻译时可转换为汉语的主动语态，译为“许多人设想…”。第—从句中，these processes指“科学的思维过程”，需译出。第二个从句中，they 指代前一从句中的these processes，翻译时需明确；by a sort of special training为介词结构作状语，前置译。

【点拨】

by no means“决不，一点也不，根本不能”。

【译文】

许多人设想，普通人的思维活动根本无法与科学的思维过程相比，认为这些思维过程必须经过某些专门训练才能掌握。