The familiar incommensurability problem

From The Psychology of the Unthinkable: Taboo Trade-Offs, Forbidden Base Rates, and Heretical Counterfactuals by Philip E. Tetlock, Orie V. Kristel, S. Beth Elson, Melanie C. Green, and Jennifer S. Lerner. From the Abstract:

Five studies explored cognitive, affective, and behavioral responses to proscribed forms of social cognition. Experiments 1 and 2 revealed that people responded to taboo trade-offs that monetized sacred values with moral outrage and cleansing. Experiments 3 and 4 revealed that racial egalitarians were least likely to use, and angriest at those who did use, race-tainted base rates and that egalitarians who inadvertently used such base rates tried to reaffirm their fair-mindedness. Experiment 5 revealed that Christian fundamentalists were most likely to reject heretical counterfactuals that applied everyday causal schemata to Biblical narratives and to engage in moral cleansing after merely contemplating such possibilities. Although the results fit the sacred-value-protection model (SVPM) better than rival formulations, the SVPM must draw on cross-cultural taxonomies of relational schemata to specify normative boundaries on thought.

If that is somewhat opaque, this is clearer.

Trade-off reasoning is widely viewed as a minimal prerequisite for economic rationality (Becker, 1981). Utility maximization presupposes that people routinely factor reality constraints into their deliberations and explicitly weigh conflicting values. Indeed, economic survival in competitive markets requires that people make at least implicit trade-offs between objectives such as work versus leisure, saving versus consumption, and consumption of alternative products. The moralist-theologian metaphor warns of sharp resistance to efforts to translate all values into a common utility metric. Fiske and Tetlock (1997) documented that, in most cultures, people are chronic "compartmentalizers" who deem some trade-offs legitimate (goods and services routinely subject to market-pricing rules) but vehemently reject others—in particular, those that treat "sacred values" like honor, love, justice, and life as fungible.

This sharp resistance is rooted, in part, in the familiar incommensurability problem. Decision theorists have long stressed that people find interdimensional comparisons cognitively difficult and resort to noncompensatory choice heuristics such as elimination-by-aspects to avoid them (Payne, Bettman, & Johnson, 1992). The moralist-theologian framework, however, treats this explanation as incomplete. Apple-orange comparisons are difficult, but people often make them when they go to the supermarket Moreover, people do not find it shameful to make trade-offs between money and consumption goods. The moralist-theologian framework traces opposition to reducing all values to a single utility metric to a deeper, more intractable form of incommensurability: constitutive incommensurability, a pivotal concept in modern moral philosophy (Raz, 1986) as well as in classic sociological theory (Durkheim, 1925/1976). As Tetlock, Peterson, and Lerner (1996) argued, the guiding idea is that our commitments to other people require us to deny that we can compare certain things—in particular, things of finite value with things that we are normatively obligated to treat as infinitely important. To transgress this boundary, to attach a monetary value to one's friendships, children, or loyalty to one's country, is to disqualify oneself from the accompanying social roles. Constitutive incommensurability can thus be said to exist whenever comparing values subverts one of the values (the putatively infinitely significant value) in the trade-off calculus. Taboo trade-offs are, in this sense, morally corrosive: The longer one contemplates indecent proposals, the more irreparably one compromises one's moral identity. To compare is to destroy.