恩格斯在关于历史唯物主义的书信中,提出了“合力论”思想,全面阐述了唯物史观的一些重要原理,弥补了过去的不足,进一步丰富和发展了历史唯物主义。科学发展观的基本内容,是在新的历史时期对恩格斯历史发展“合力论”的继承和发展。 In his letters about historical materialism, Engels proposed the idea of ​​“allied forces”, comprehensively expounded some important principles of historical materialism, made up for the deficiencies of the past and further enriched and developed historical materialism. The basic content of the scientific concept of development is to inherit and develop Engels’ historical development “allied forces ” in the new historical period.