The presented article is devoted to using present-day legal terminology in scientific research on pre-modern and pre-constitutional states’ legal systems. The main focus of analysis is the rule of law principle existence between the 16th and 18th centuries in the Polish-Lithuanian Commonwealth. The author tries to establish whether this is even justified to use the modern idea of the rule of law to describe the Polish-Lithuanian pre-partitions political system? And, if so, how technically do that to avoid presentism? The author tries to formulate a set of features concerned with the rule of law principle applicable to the Polish-Lithuanian Commonwealth. He also tries to determine the set of conditions necessary for the rule of law principle to blossom in pre-modern reality fully