Expression, in Goodman's technical analysis, is exemplification operating through metaphorical transfer. A grey painting is not literally sad—sadness is a property of conscious beings, not of pigment on canvas. But the painting can be metaphorically sad, possessing sadness as a transferred property from the domain of human emotion to the domain of visual properties. The transfer occurs through conventions that associate certain formal features (grey tonality, downward compositional movement, spatial emptiness) with certain emotional qualities. The painting exemplifies the metaphorically possessed property—it is sad and directs attention to its sadness—and the viewer who perceives the expression gains understanding of the emotional quality through the specific visual means by which it is conveyed. Expression is not the artist's communication of her emotions to the viewer—Goodman rejected the transmission model of aesthetic emotion as psychologistic. It is the work's metaphorical possession of properties that the symbol system makes referentially available, and the cognitive value lies in the understanding the viewer achieves by attending to how the formal properties carry the metaphorical qualities. The understanding is irreducible: what the painting teaches about sadness through its particular grey is not statable propositionally without becoming a different kind of knowledge.
Goodman's account of expression dissolved the Romantic theory that treated artworks as vehicles for the artist's emotions. The grey painting is not sad because the painter was sad when she made it. It is sad because the formal properties metaphorically possess sadness according to conventions the culture has established through centuries of looking at grey paintings and finding them expressive of somber emotions. The painter may have been perfectly cheerful; the painting is still sad, if it possesses and exemplifies the formal properties that convention associates with sadness. The expression is a property of the work, not of the artist, and it is available to viewers who know how to perceive metaphorical possession even if they know nothing about the artist's biography.
The metaphorical possession is grounded in literal possession in a different domain. For a painting to be metaphorically sad, sadness must exist literally somewhere—in human emotional experience—from which it can be transferred. The transfer depends on the existence of both domains: the literal (human consciousness capable of sadness) and the metaphorical (visual properties organized to possess sadness metaphorically). AI-generated images can produce outputs with formal properties that convention associates with emotional qualities—a diffusion model can generate grey tonalities, weighted compositions, spatial emptiness. Viewers may perceive these images as expressing sadness. But Goodman's framework asks: Is the expression right? Does the metaphorical possession achieve the fit between visual means and emotional content that constitutes genuine expression, or does it merely simulate expression by deploying conventional associations without the worldmaking project that gives expression its specificity?
The question cannot be answered by examining the image in isolation. Rightness of expression depends on fit with the worldmaking project—an artist constructing a grey image as part of sustained engagement with loss embeds the expression in purposes that give it referential precision. The sadness expressed is not generic; it is this artist's configuration of formal means to render this experience of loss. An AI-generated image with identical visual properties has no comparable project. It has a prompt and a probability distribution. The expression, if it is expression at all, floats free of the project-specificity that makes expression cognitively valuable rather than merely conventionally correct. It is sadness without a griever—form without the experiential content that gives form its expressive weight.
Expression is analyzed in Languages of Art, Chapter II, section 5. Goodman built on his account of metaphor (developed earlier in 'On Likeness of Meaning,' 1949) to show that expression is not a unique aesthetic relation but a species of exemplification—specifically, metaphorical exemplification. The analysis was designed to replace vague talk about artworks 'conveying' or 'communicating' emotions with a precise account of how formal properties can refer to emotional qualities through established metaphorical transfers. The framework has become foundational in analytic aesthetics, though debates continue about whether Goodman's anti-psychologistic approach adequately captures the role of artistic intention and emotional engagement in aesthetic experience.
Expression is metaphorical exemplification. Works express qualities they metaphorically possess—a painting is sad not literally but through a transfer from the emotional to the visual domain, exemplifying the transferred property.
Conventional, not natural. The metaphorical transfers connecting formal properties to expressive qualities are conventional—learned through immersion in a culture's aesthetic practices, not perceived immediately.
Requires both literal and metaphorical domains. For a work to express sadness, sadness must exist literally (in human experience) to be transferred; expression depends on the worldmaker's grounding in lived emotion.
AI simulates without grounding. AI-generated works can deploy conventional expressive properties (grey tonalities for sadness) without the experiential grounding that gives expression its rightness—form without substance.