维特根斯坦在中期哲学中探讨了有关语句证实与语句意义的问题，可称作是维特根斯坦的证实思想。虽然无法对其准确定义，但不可否认这是出现于20世纪30年代早期的思想探索，一方面是通过对前期哲学的批判展开自身理论内容，以对真值条件理论与图像论的批判与继承为主，实现了由追求真到追求意义的转变；另一方面是他与维也纳小组之间的交流促使他的思想转变。由于证实思想出现于维特根斯坦思想发展的特殊时期，因而其内容并非完全孤立出现，而是与其所处的现象语言和哲学语法思想形态密切相关，并在不同的思想形态上展现出了不同的具体内容。从现象语言到哲学语法的转变，表明他的证实思想随着中期哲学发展而不断改变，展现出中期哲学思想形态之间纵横交错。同时，证实思想内容的不断变化，促使我们从不同维度考察它的方法论价值、与感觉经验的关系以及语言使用的维度。尽管证实思想因内容上的动摇和对中期哲学阶段的依附而导致他在后期哲学中终被放弃，但这一思想对于我们清晰理解维特根斯坦中期哲学以及他的哲学发展，可谓不可或缺。

In his Middle Philosophy, Wittgenstein studied on the issue of the sense of proposition and its method of verification, which we called the thought of verification, or verificationism. This thought emerged in his philosophy around the late 1920s and the early 1930s, and this timeline indicates that this thought unfolded itself through the rejection the picture theory and the truth-conditional theory in his early philosophy, which is actually a change from the pursuit of truth to the pursuit of sense, on the one hand, and that the Vienna Circle inspired Wittgenstein to form this thought in the first place, on the other hand. As the middle philosophy changes gradually, verificationism changes its content and manifests the crisscross of various ideas during the middle philosophy, especially the idea of phenomenological language and philosophical grammar, whose relations with verificationism outstood in this period.In the meantime, the study of verificationism entails three perspectives: methodological tool, sense-data and experience, the language use. Due to the indeterminacy of its content and its dependence of middle philosophy, verificationsim was finally abandoned by Wittgenstein when he moved foward into his late philosophy. Nevertheless, to the understanding of middle philosophy and even the whole philosophy of Wittgenstein, it is indispensable.