In this account, classical liberalism leads naturally to Austrian economics and modern libertarianism. That sequence is useful but incomplete.

Liberty developed through the convergence of two lineages. The first is the modern lineage of Enlightenment criticism, which required political power to justify itself before reason. The second is an older realist tradition, running from Aristotle and Thomas Aquinas through the School of Salamanca, Richard Cantillon, Carl Menger, Eugen von Böhm-Bawerk, Ludwig von Mises, and Murray Rothbard. These thinkers did not form a single school, nor did they agree on every question. What connects them is a shared orientation: reality has an intelligible order, human action has a structure, and political power cannot be abolished either by command.

The relevant difference is not between the Enlightenment as a whole and an older tradition, nor between reason and faith. Important currents within the Enlightenment, especially the Scottish Enlightenment, recognized that custom, law, money, and markets could arise without deliberate design. The deeper conflict is between a constructivist current within modern thought and an older causal-realist approach to social order. Friedrich Hayek identified the pinnacle of this constructivism as the "fatal conceit," the erroneous belief that man is able to shape the world around him according to his wishes. The realist tradition emphasizes the intelligibility and causal structure of social phenomena, while the constructivist tendency places greater confidence in deliberate organization and direction.

The danger appeared when criticism of inherited institutions hardened into confidence in consciously-designed ones. Locke was not Marx, and constitutional government was not socialism. The continuity lies in method: once social order is treated primarily as an artifact of design, political disagreement increasingly turns on the identity of the designer, the objective of the plan, and the permitted range of control. This tendency appears in social planning, price controls, central banking, licensing, regulation, and the administrative management of economic life.

The older lineage begins from a different premise. Aristotle started with beings as they are and the ends toward which they tend. Human beings choose, deliberate, employ means, form households, exchange goods, and enter associations. Thomas Aquinas carried this realism into law and politics. A command does not become just simply because a ruler issues it. Human law derives its normative order from principles that political authority does not itself create.

Many late Scholastics, particularly the Spanish Scholastics associated with Salamanca, extended this framework to property, exchange, money, and political authority. They increasingly identified the just price with common estimation, shaped by utility, scarcity, and market conditions, rather than with an objective measure of production costs. By situating economic phenomena within moral agency and commutative justice, they placed limits on the arbitrary exercise of political authority in economic life. Within this tradition, thinkers such as Juan de Mariana also articulated strong limits on taxation, confiscation, and monetary debasement.