<p>This paper proposes a protocol to investigate preferences for unconditional basic income (UBI) through the lens of social preferences. Bridging economic philosophy and experimental economics, the design builds on the conceptual link between Van Parijs’s theory of justice, rooted in Rawlsian maximin reasoning, and social preference types such as maximin, efficiency, and inequality aversion. While a few previous studies have applied Rawlsian or Van Parijsian reasoning in laboratory settings to elucidate preferences for UBI, they often suffer from limited sample sizes, lack of monetary incentives, or incomplete theoretical frameworks. Broader empirical approaches, such as cross-sectional surveys, field experiments and referenda, offer insights into political feasibility but struggle to capture individuals’ underlying normative reasoning and are highly sensitive to context and framing. Responding to these limits, the protocol adopted here is modular and adaptable, allowing researchers to test various redistributive schemes, framings, or funding mechanisms. Beyond the UBI case, this framework contributes to a broader reflection on the understanding of fairness in distributive choices.</p>