This is the 4779th most frequent Japanese word.
正統
Orthodox; legitimate; traditional.
In this sentence, '正統的' (seitouteki, orthodox) is used as an adjective to describe the traditional or conventional correctness of something, in this case, a way of thinking.
彼の考え方は正統的なものであると言える。
His way of thinking can be said to be orthodox.
The term '正統' (seitou, legitimate) here conveys legitimacy or rightful representation, especially in relation to sovereignty or authority.
正統な王位継承者が現れた。
A legitimate heir to the throne has appeared.
'正統の' (seitou no, orthodox) modifies '思想' (shisou, ideas), indicating adherence to established and recognized principles.