Abstract: After the rise of positivism paradigm,philosophical speculative research has been criticized for its subjectivity.The essence of positivism research is to make use of information and data collected to explore and discover new things or the relationship between things,which should be the same for philosophical speculative research.As for the latter,a lot of information and data are tacit,and such tacit evidence serves as an important type of evidence in philosophical speculative research.The application of tacit evidence is of vital necessity for the expression of philosophical speculative research.There are two types of tacit evidence:those which need to but cannot be expressed and those which can but do not need to be expressed.The application of tacit evidence is conducive to enhance the research value of abstract general problems,to make the demonstration of value issues possible,to make the discourse expression of humanities and social sciences more economical,and to further improve the rational level of human thinking.However,in the process of applying tacit evidence,people are prone to encounter obstacles in understanding the meaning of texts,which not only leads to bias or ambiguity when reading,but also gives rise to researchers' subjective arbitrariness,as well as empty and shallow debates.The value of tacit evidence in philosophical speculative research is undeniable,and we should guard against its misuse and abuse in the research of humanities and social sciences.

Key words: tacit evidence, philosophical speculation, objective knowledge, objectified knowledge, methodology