The understanding of human beings to causal relations has defects

which limts the rationaity and avail-ability of policy thinking. In China

the thinking defection is partly due to formal logic

especially

the theoryabout medus ponens. The theory about modus ponens in the traditional formal logic separates the relation ofcondition and result into four types: full conditions

essential conditions

full and essential condtions

andhidden condition. As a true system of causal relations takes shape

which separates causes into four types

such as full causes

essential causes

full and essential causes

and hidden causes. The traditional typology ofcausal relations loses partial causes

which may partly lead to a lot of different meanings

confusion and lacksof thought

discussion and policy. The author brings out a new system of typology of causal relations

whichseparates causes into five types as follows: full causes

essential causes

full and essential causes

partialcauses

and hidden causes. The next investigation is to expound and prove its completeness

which consists ofinclusion and alternative

and count the probability of all the kinds of causal relations. The author holds thatthe goal is to build more ecientific poicy - thinking mode. As the formal logic traditionally doesn’ t regardcausal relations or policy - thinking mode as major object of study

the paper doesn’ t belong to the category offormal logic. The author tries to pass through thinking methods

formal loglc

scientific methedology

policyscience and all the positive subjects related to causal judgment.