因为上古汉语没有专职判断词,名词与名词性词语不需判断词即可构成判断句,又由于“是”与指代词“此”有相同的指代用法,因此上古“知之为知之,不知为不知,是知也”类“是”被认为是与“此”相同的指示代词。上古曾有“兹”“之”“斯”“是”“此”等一组词具有指代用法,但只有“是”后来发展为判断词,“此”至今仍为指代词。为什么同是指代词却只有“是” Because ancient Chinese does not have full-time judgment words, nouns and nominal words do not need to judge the word to form a judgment sentence, and because “yes ” has the same reference to the pronoun “this ”, so the ancient For the sake of knowing, I do not know, I do not know, is also known as “class ” is “is considered to be the same demonstrative pronoun as ” this “. In ancient times, a group of words such as ”“ ”“ ”“ ”is “ ”this “This ” is still a pronoun. Why is the same pronoun? Only “is ”