The System of Acquired Rights: A Reconciliation of Positive Law and the Philosophy of Law

Lassalle argues that the concept of 'acquired right' is the defining political and social idea of the modern period. Against conservative theorists who treat existing property relations as sacred and inviolable, he contends that law is a continuous expression of a nation's evolving consciousness of right. No generation can bind a later one to its own conception of right. What one age acquires through voluntary action, a later age may legitimately abolish if its own sense of right demands it. The book thus provides a philosophical justification for revolution.

Lassalle formulates two principles. First, no law may have retrospective force if it affects the individual only through and in virtue of his voluntary actions . Second, any law may have retrospective force if it affects the individual without the intervention of any such voluntary act . The key is the individual's freedom and responsibility: when a person acts voluntarily under existing law, the state cannot later punish or invalidate that act without violating the person's autonomy. But rights that arise from status or law rather than individual action are always subject to change.

Lassalle argues that the French Revolution was legitimate because it did not violate acquired rights. When the Assembly decreed that feudal obligations were abolished from July 14, 1789, it developed principles already proclaimed by the nation on that day, without extending the law to inheritances opened before that date . The revolution was not an arbitrary seizure of property but the expression of a new national consciousness of right. As one scholarly analysis puts it, Lassalle justifies revolutions as a process of 'abolition-acquisition' of rights by citizens .

Marx rejected Lassalle's entire framework as idealist and juridical rather than materialist. Bernstein notes that although Lassalle was acquainted with Marx's Critique of Political Economy, there is not a single line in The System that could be interpreted in Marx's sense that legal relations are rooted in economic life conditions . Marx and Lassalle corresponded about inheritance law, but Marx objected to Lassalle's claim that the Testament could only be explained by Roman mythology and the Roman idea of immortality, insisting instead that Roman private property and the disruption of consanguineous groups were the real ground of the Roman testament .

Lassalle directed his attack primarily at Friedrich Julius Stahl, the conservative legal philosopher who argued that all existing social order and the rights arising from it were inviolable and sacred. Lassalle replied that just because every age is autonomous, no age can be subject to the domination of another; no age is bound to permit the continuance as right of anything that contradicts its own consciousness of right . He also attacked the 'spokesmen of the liberal bourgeoisie' for their superficial and isolated conception of politics .

The second volume examines Roman and Germanic inheritance law historically and philosophically. Lassalle argued that the Roman testament corresponded to the Roman Volksgeist and the idea of the immortality of the will-subject, while the old Germanic intestate law corresponded to the Germanic Volksgeist of family unity based on love . However, he concluded that modern intestate succession and testamentary law are no longer natural rights but state institutions, subject to regulation by the general will of the state . This historical analysis served his broader argument that legal forms are products of national spirit, not eternal categories.