What new mentality spread throughout europe after 1848 and rejected idealism in favor of tough-minded realism aimed at strengthening the state and tightening social order?

Realpolitik.

Explanation:

The new mentality that spread throughout Europe after 1848 and rejected idealism in favor of tough-minded realism aimed at strengthening the state and tightening social order was realpolitik. In Europe after 1848, the romantic and idealistic ideas and the utopian dreams gave place to materialism. Realpolitik was based on pragmatism, not on ethical ideals. It was also called the politics of reality. People's interest turned to science and this way of thinking influenced Europe in the 19th century.

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