he asserted, also, that his power to follow a long and purely abstract train of thought was very limited, for which reason he felt certain that he never could have succeeded with mathematics.重点词汇assertvt. 维护，坚持；断言；主张；声称purelyadv. 纯粹地；仅仅，只不过；完全地；贞淑地；清洁地abstractadj. 纯理论的；抽象的；抽象派的n. 摘要；抽象；抽象的概念；抽象派艺术作品v. 摘要；提取；抽象化；退出；转移；使心不在焉句式分析句子的主干结构是：he asserted that 引导的宾语从句。that 引导的宾语从句的结构是：h

is power (主语) + was (系动词) + limited (表语)，其中不定式 to follow … of thought 做定语修饰从句主语 power。for which reason 引导的非限制性定语从句修饰前面整个句子。其中，又包含一个由 that 引导的宾语从句。参考译文他还坚持认为自己进行长时间纯抽象思维的能力十分有限，由此他也认定自己在数学方面根本不可能有大的作为。