Why are beauty and ugliness difficult to define in aesthetics?

In the field of aesthetics, defining beauty and ugliness is notoriously difficult because these terms are often too vague and subjective to categorize the world successfully. Because almost anything can be perceived as beautiful from a specific point of view, the terms may function more as expressions of personal attitude than as objective qualities.1

Philosophers have struggled to find a precise definition for these concepts for several reasons:

• Subjectivity vs. Universality: Aesthetic judgments are rooted in immediate sensory experience, yet they are often expressed as if they were objectively valid for all rational beings. This creates a paradox: one cannot be "talked into" finding something beautiful, yet we often seek universal agreement for our aesthetic preferences.2
• Contextual Dependence: Our sense of beauty is rarely abstract; it depends on our conception of the object. For example, features considered beautiful in a horse may be viewed as ugly in a human, as our judgments are governed by our understanding of what those subjects are and how they function.3
• Lack of Clear Criteria: Attempts to define beauty—such as the Scholastic focus on proportion and clarity or the Neoplatonist emphasis on mathematical harmony—often become circular, as "worse" arrangements are simply defined as "less beautiful".4

Ultimately, because aesthetic experience involves a complex, often paradoxical synthesis of sensory perception and intellectual judgment, these concepts remain elusive and resistant to simple, universal definitions.2