"Now obviously the propositions of the system have reference to matters of empirical fact; if they did not, they could have no claim to be called scientific"

This quote by Talcott Parsons is referring to the idea of a scientific system. A scientific system is a set of proposals that are based on empirical facts, meaning truths that can be observed and evaluated. Parsons is saying that if a system of propositions does not have any reference to empirical realities, then it can not be considered scientific. This is because scientific systems are based upon truths that can be proven and evaluated, rather than just theories or concepts. For that reason, if a system of proposals does not have any recommendation to empirical realities, then it can not be considered scientific. This quote by Parsons emphasizes the importance of empirical facts in scientific systems, and how they are necessary for a system to be thought about clinical.