Keeping these tenets in mind, positivists set for themselves a programme by adopting which they thought they could defend the principle of induction in the fact of the formidable attack made by Hume. As inductivists, they were obliged to ward off the ghost of Hume by showing that the principle of induction can be rationally justified. Positivists asserted that scientific observations are in principle theory-free and therefore are indubitable. Observations or facts are prior. Theories which are their interpretations are posterior. These observations constitute the bedrock on which the theoretical edifices of science rest. The edifices constituted by theories are arrived at by using the principle of induction. Now, positivists thought that if they could show that the inductively arrived at scientific theories are related in certain specifiable ways to the bedrock constituted by indubitable observations, they would succeed in establishing the rationality of our belief in the principle of induction. Critique of positivists' programme collapsed like a house of cards. Not only did they fail to identify the specific way in which observational substructure and theoretical superstructure of science were related but they also dismally failed to show that our observations are or can be shown to be theory-free and therefore indubitable. The opponents of positivism convincingly showed that the idea of “pure” or theory-independent observation was a myth. Telling arguments were advanced to show that all observations are theory-dependent. It may be noted that positivism dominated the scene during the bulk of the first half of the twentieth century. But, every tenet of positivism has been successfully called into question by subsequent developments. The first tenet of positivism to fall was the one concerning the idea of “pure” observation. It is interesting to see in this connection how the critics of positivism exploded the myth of “pure” observation by showing how our observations presuppose theory. We may mention a couple of arguments in this connection.