Robert Alexy has for many years been a prominent analyst of the role of principles in legal argumentation, and an equally prominent defender of the rationality of balancing and proportionality modes of legal decision-making. But although Alexy's defense of proportionality and balancing against charges by Jurgen Habermas and Justice Antonin Scalia that balancing is essentially an irrational process is sound, Alexy in the process is too quick to collapse the important differences between the process of balancing competing principles and the process of interpreting a canonical written text. Although both can be and are frequently rational, rationality is not the same as external constraint, and the ability of canonical texts to provide a degree of external constraint on legal decision-making that cannot be provided by open-ended principles is a difference that should not be lost in the well-aimed efforts to demonstrate that both can be rational and both have important places in legal argumentation and decision-making.

Citation
Frederick Schauer, Balancing, Subsumption, and the Constraining Role of Legal Text, in Institutionalized Reason: The Jurisprudence of Robert Alexy, Oxford University Press, 307–316 (2012).