Introduction: Democritus’s terse aphorism that ‘if anyone oversteps the measure, the most pleasurable things become most unpleasant’ raises a question that transcends its ancient Greek context: what does it mean to transgress due measure, and how can such a transgression be discerned across different domains of existence and making? One of the most sustained and philosophically rich answers to this question emerges from the Iranian intellectual tradition, where the concept of moderation (iʿtidāl) functions as a foundational ontological and aesthetic principle. While secondary literature has typically confined moderation to the ethical sphere, as a moral mean between two extremes, Avicenna radically redefines it: iʿtidāl is not merely an ethical virtue but a dynamic ontological principal binding being to beauty.
Objectives and Questions: The main research questions are: What ontological status does moderation, as an aesthetic property, possess in Avicenna’s philosophical system? And how does the concept manifest concretely in domains such as crafts and natural things? Answering these questions sheds light on the philosophical presuppositions underlying artistic creation in the Iranian-Islamic world and yields a systematic understanding of the bond between being and beauty in that tradition.
Method: To develop this line of inquiry, the study adopts a philosophical, text-based approach and traces moderation as an aesthetic property across two interconnected domains. The first explicates its ontological mechanism within Avicenna’s system. The second illustrates how moderation becomes concretely manifest in natural and artificial objects.
Findings: The first domain, the ontological mechanism, finds its clearest articulation in Avicenna’s al-Najāt, which furnishes the foundational formulation: “The Necessary Existent is pure beauty and splendor, and It is the principle of all moderation. For every moderation occurs in a multiplicity of composition or mixture, and brings about a unity in its multiplicity.” With this statement, moderation is lifted beyond the ethical sphere and repositioned as a link in the chain of existential emanation, one that begins with pure unity and terminates in the ordered, determinate multiplicity of the material world. The same passage supplies Avicenna’s criterion of beauty: “The beauty of each thing lies in its being as it ought to be.” In Avicennan ontology, it is form (ṣūra) that determines the ‘fitting state’ and optimal perfection of each existent. Beauty therefore results from a threefold process. First, form, the determining principle that unifies matter and directs it towards perfection, defines the thing’s ‘fitting state.’ Second, moderation is the means by which form imposes proportion and equilibrium on material multiplicity, preventing disorder and establishing necessary, harmonious relations between parts and whole. Third, ‘unity in multiplicity’ is the direct outcome of moderation’s action: matter, now determined by the specific form, becomes an integrated, unified, and individuated whole, precisely the whole that form antecedently demanded. Because this state exactly corresponds to ‘being as it ought to be,’ beauty is actualized.
Moderation’s ontological function finds concrete expression in both natural and artificial objects. In the human body, moderate temperament serves as the foundation of health and facial beauty; Avicenna traces aesthetic defects directly to ill temperament (sūʾ al-mizāj) and establishes a systematic link between beauty of form (ḥusn al-ṣūra) and beauty of character (ḥusn al-sīra). Moderate temperament, by grounding the intellect’s dominance over the animal faculties, enables the formation of virtuous dispositions. The resulting excellence of character constitutes a harmony with the divine order, and its effects become visible in outward appearance. In music, the three-part division of the quadruple (dhī al-arbaʿ) exemplifies ‘excellence of choice’ (ḥusn ikhtiyār), avoiding the excess of heaviness and difficulty, and the deficiency of slackness of the soul. In poetry, moderation governs both form, balanced rhyme length and proportion among phonetic stretches, and meaning, which must avoid strained metaphors and fallacious expressions. In rhetoric, sentence length must be preserved from excessive brevity, which leads to oversight and inattention, and from excessive length, which brings about tedium and forgetfulness; rhymed prose achieves structural and semantic balance through ‘roundedness’ (istidāra).
Results Bridging ontology, ethics, medicine, and the theory of art, moderation is a formal, objective, and dynamic quality in a composite whole, one in which the constituent parts are arranged according to a rational measure proportionate to the specific perfection of the thing, avoiding excess and deficiency, achieving a harmonious equilibrium perceptible to the senses or the intellect, and culminating in ‘unity in multiplicity.’ It is the most fundamental criterion of beauty in the Iranian tradition.