— Knowledge is divided in two category of personal and attainment sciences according to being mediate or absence of mediate for achievement. In fact attainment sciences are such science which needs some mediates. But personal science is knowledge about things without need to mediate.According to above definitions, it seems that the role of observation in creation of attainment sciences is more than its place in personal science. But various inferences such as induction, revocable, etc. in practical philosophy imply that observation by no means can be a base for achievement in practical science. At the same time, base for personal science is according to observation (if there is no error) can be a factor to reach to the truth without mediate.

Keywords