Popper believed that social science could be scientific, but that that social scientific knowledge has to be based on deduction and falsification (rather than induction and verification).
For Popper, sociology can be scientific if it makes precise predictions through the use of the hypothetic-deductive model.
In the hypothetic-deductive model, researchers start with a specific, testable, hypothesis, then they collect data, analyse it, and either confirm the hypothesis based on their evidence, or reject it and start the process over again. If a hypothesis is proven, then a theory may be derived which will form the basis of future research.
The principle of falsification means researchers deliberately look for evidence that could disprove their hypothesis.
In the above model, ‘grand theories’ such as those put forwards by Marxism are not specific enough to be tested.
The implications are that if sociology wants to be regarded as a science it must limit itself to research questions which can be turned into clear hypotheses and tested by others.
Unlike Durkheim, Popper believed that we can never verify laws of human behaviour because it’s always possible to find future evidence which could falsify existing social theories.
Comparison of Popper and Durkheim
Durkheim argued that science, and social science should be inductive and based on verification.
Popper argued that science and thus social science were based on deduction and falsification.
Induction = looking at the evidence and developing a theory from that evidence
Deduction = starting with a theory and testing it by working out what evidence would verify or falsify it.
I have summarised this from Chapman 2015, which in turn is obviously summarised from Haralambos edition 8.