Adjective + 性 = abstract noun: 正确 'correct' + 性 'quality of' = 'correctness'. The same template gives 重要性 'importance', 可能性 'possibility', 灵活性 'flexibility' - extremely productive in academic and technical writing.
culture
Example 2 paraphrases Deng Xiaoping's 1978 motto 实践是检验真理的唯一标准, the editorial that signalled the shift away from Mao-era ideology. The phrase is so canonical that any line beginning 实践是检验真理 will be read as quoting it.
