Positivism holds that truth is knowable according to universal, general laws. In contrast, social constructivism argues that what counts as truth depends on the social and cultural contexts of the inquirers.
According to positivism, knowledge should be gathered through observation and testing hypotheses, subject to the scientific test of falsifiability. From the perspective of social constructivism, however, the decision to reject any particular theory on the basis of it being falsified requires a value judgment shaped by culturally conditioned beliefs.
In positivism, scientific knowledge is that which can explain and predict. The outcomes of experiments can be repeated when initial conditions are met. Social constructivism, on the other hand, claims that the conditions for observing phenomena change as societies develop new institutions and revise cultural values, leading to differences in how data are interpreted.
Positivism is considered reductionist because it views knowledge as a body of facts, each of which may theoretically be taken independently of any other, and the apparent unity of sensory experience as reducible to its constituent components (electrochemical, subatomic, and so forth.) Social constructivism, on the other hand, emphasizes the holistic, relational and interdependent character of any subject of scientific inquiry.