Positivist believes that the goal of knowledge is simply to describe the experiential phenomena while postpositivist recognizes that scientific thought and work are not distinct to daily activities. In context of consumer behaviour studies, Post-Positivism paradigm of epispemology is more suitable.
For detail please read:
Hacking, Ian. (1983). Representing and Intervening, Introductory Topics in the Philosophy of Natural Science, Cambridge, UK: Cambridge University Press.
Creswell, J.W. (2013). Qualitative inquiry & research design: choosing among the five approaches. Thousand Oaks, CA: Sage Publications, Inc.
Positivism holds that reality is “out there”: and so, the intention of positivists is to discover immutable universal laws. Post-positivists suppose that reality is "out there" but believe that its assessment is always subject to conjecture because the background knowledge, hypotheses, theories, and/or values of researchers can influence what is observed. In consumer behavior studies (and elsewhere), the reign of positivism ended in the 20th century: competing explanations come from critical theory, ethical theory, ethnography, feminism, interpretivism, postmodernism, post-structuralism, and semiotics, to name a few.
Positivism is an epistemological position that holds that the goal of knowledge is simply to describe the phenomena that we experience. The purpose of science is sticking to what we can observe and measure. Knowledge of anything beyond that is impossible. In the positivist view, the universe is deterministic. It operates by laws of cause and effect that we could discern if we apply the unique approach of the scientific method. Science is largely a mechanical affair. The key approach of the scientific method is the experiment, the attempt to discern natural laws through direct manipulation and observation.
However, since the middle part of the 20th century things have changed in our views of science. Probably the most important has been our shift away from positivism into what is called post-positivism. Postpositivism recognizes that the way scientists think and work and the way we think in our everyday life are not distinctly different. Scientific reasoning and common sense reasoning are essentially the same process. There is no difference in kind between the two, only a difference in degree. Postpositivism recognizes that all observation is fallible and has error and that all theory is revisable. Where the positivist believed that the goal of science was to uncover the truth, the post-positivist believes that the goal of science is to hold steadily to the goal of getting it right about reality, even though we can never achieve that goal.
The difference between the paradigm of modernism and postmodernism is that postmodernism defines science on the basis of diversity and fragmentation. Like a collage painting composed of different parts, postmodernism questions the standardization of modernism. They standardize based on their own ideas. They frame themselves with long narratives. Postmodern theory was formed from the school of neo-Marxism. Thoughts that believe in the conflict of interests in human societies are based on this. Owners and owners of factories, not for the benefit of workers. For more information, see Dr. Marie Joach's book on organization theory.
Positivists believed that objectivity was a characteristic that resided in the individual scientist. Scientists are responsible for putting aside their biases and beliefs and seeing the world as it 'really' is. Post-positivists reject the idea that any individual can see the world perfectly as it really is.
Positivism refers to an evidence-based reality that can be mathematically interpreted. The post-positivist paradigm evolved from the positivist paradigm. It is concerned with the subjectivity of reality and moves away from the purely objective stance adopted by the logical positivists (Ryan, 2006).
Positivism Vs interpretivism are polar extreme of quantitative Vs qualitative research methodology. Post-positivism is a refined method that acknowledges biases in whatever method that is being chosen and therefore more interpretive.