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.
[核心词汇]
assert(v.)坚持；断言// abstract (a.)抽象的；(v.)提取，抽取；(n.)摘要// a train of 一系列
[结构分析]
本句的主干结构为he asserted that…（他断言……），that引导宾语从句，宾语从句的主干为his power was very limited（他的能力十分有限），to follow a long and purely abstract train of thought（进行长时间纯抽象思维）为power的后置定语。for which reason he felt certain that…（正因为如此，他确信……）为非限定性定语从句，修饰前面的his power…was very limited。定语从句中又包含that引导的宾语从句that he never could have succeeded with mathematics（他在数学方面不可能取得成功）。
[翻译技巧]
不定式结构to follow...thought 作power的后置定语，翻译时可采用前置法，放在被修饰的名词之前。for which reason引导非限定性定语从句，在从句中作状语，可译作“因此，正因为如此”，这个定语从句又嵌套that引导的宾语从句，宾语从句的谓语动词never could have done是对过去发生动作或状态的推测，表示“不可能做过”的含义。
[参考译文]
他还断言，自己进行长时间纯抽象思维的能力十分有限，正因为如此，他确信自己在数学方面不可能取得成功。
