How can a silent, material universe contain properties that command us to act? To dismiss J.L. Mackie’s claim of "queerness" as mere incredulity misses the profound challenge he poses. When properly reconstructed, the argument from metaphysical queerness is not a superficial complaint about weirdness; it is a sophisticated demand for ontological parsimony and explanatory coherence. It asks how objective, prescriptive properties can possibly integrate with our modern, scientific understanding of the natural world.
## The Core of the Steel Man: Intrinsic Motivating Power
To steel-man the metaphysical branch of the [Argument from Queerness](https://en.wikipedia.org/wiki/Argument_from_queerness), we must articulate the precise nature of the "strangeness" Mackie identifies in *Ethics: Inventing Right and Wrong* (1977). The strength of the argument lies in the unique dual-nature of objective moral values: they must be simultaneously *objective* (part of the fabric of the world, independent of us) and *prescriptive* (intrinsically action-guiding).
In modern analytic philosophy, this is formulated as a clash between realism and the Humean theory of motivation. As the eminent moral philosopher Richard Joyce notes in [*The Myth of Morality*](https://cambridge.org/core/books/myth-of-morality/7E2404A81E99596B8B4E639A68367F68), normal external facts are descriptive; they require an internal desire (a "conative state") to move us to action. For example, the fact "it is raining" only moves me to grab an umbrella if I *desire* to stay dry.
However, objective moral properties must possess what Mackie called "to-be-pursuedness" built directly into them.
> "An objective good would be sought by anyone who was acquainted with it, not because of any contingent fact that this person, or every person, is so constituted that he desires this end, but just because the end has to-be-pursuedness somehow built into it."
> — J.L. Mackie, *Ethics: Inventing Right and Wrong*
To-be-pursuedness requires a magnetic, motivational force that exists independently of human desires, yet acts directly upon human agency. This violates our best metaphysical theories of how the physical world interacts with mind and agency.
## Supporting Foundations: The Supervenience Problem
The strongest support for metaphysical queerness comes from the problem of **supervenience**—how moral properties relate to natural properties. If an act of cruelty is objectively wrong, the "wrongness" is not a physical property like mass or velocity. Instead, it must "supervene" or hang upon the natural facts (the infliction of pain).
A sophisticated defender of Mackie, such as philosopher [Stephen Yablo](https://en.wikipedia.org/wiki/Stephen_Yablo), would argue that this supervenience relation itself is metaphysically baffling. Why should a entirely different, non-natural property of "wrongness" inevitably and necessarily emerge from a specific configuration of physical matter? In any other domain of science, relations between different levels of reality (like chemistry emerging from physics) are causally and logically explicable. Moral supervenience, by contrast, requires a unique, brute, and unexplainable metaphysical glue.
## Defending Against the Realist Rebuttal
The most formidable objection to Mackie comes from "Cornell Realists" like Nicholas Sturgeon, who argue that moral properties are simply complex natural properties, no stranger than biological or psychological states.
A sophisticated defender of queerness responds by pointing out that biological states do not carry intrinsic, categorical imperatives. A biological state can tell us what *is* happening, but it cannot contain an inescapable, authoritative *ought* that binds an agent regardless of their goals. By stripping moral properties of their categorical authority to make them fit into the natural world, the realist ceases to talk about *objective values* at all, effectively conceding Mackie's point.