Some historians consider the late nineteenth century and early twentieth century to have been crucial decades in the development of Western thought. What evidence supports that contention?

Hi. You did not enter the text to which this question refers, which makes it impossible for your question to be answered. However, I will try to help you as best I can.

A textual evidence is a justification that the author uses to prove an argument presented in the text. This evidence seeks to present elements that prove that the author's argument about something must be considered correct and true. In this case, to answer your question, you should read the entire text and identify the sentences the author uses to prove that the late nineteenth and early twentieth centuries were crucial decades in the development of Western thought. In this case, the author can present the scientific discoveries made during this period that were essential to explain and solve several problems that humanity did not know how to solve.