Book: On the Unchangeableness of God

Overview
Philo of Alexandria presents a sustained defense of God's immutability, arguing that the divine nature is perfect, simple, and beyond all change. Drawing on Scripture and Hellenistic philosophy, Philo insists that any biblical language suggesting divine alteration must be interpreted in light of God's absolute unchangeableness. For him, true theology protects the unity and permanence of God from anthropomorphic readings that would ascribe passions, errors, or temporal processes to the divine.

Philo's central claim
God is entirely immutable because change implies deficiency, potentiality, or time, none of which can attach to a perfect being. Change presupposes becoming from one state to another, but perfection is completeness without transition. Philo therefore makes a sharp distinction between God as the transcendent, simple source of being and the mutable realm of sensible things; only the latter participates in temporal flux. Any appearance of divine change must be read as metaphor, accommodation, or as describing effects within creation rather than alterations in God.

Scriptural interpretation
Philo approaches problematic biblical passages, texts that speak of God "repenting," "being angry," or "changing his mind", through allegory and philosophical principle. Anthropomorphic expressions are treated as pedagogical devices tailored to human capacity, designed to teach moral and salvific truths in language that finite creatures can grasp. When Scripture states that God relents or is grieved, Philo reads those phrases as referring to changes in human beings or in the external world rather than ontological changes in God. Thus divine wrath indicates a moral response registered in creatures, not a mutable passion in deity.

Philosophical resources
Philo fuses Jewish exegesis with Stoic and Platonic vocabulary, using notions of simplicity, unity, and the timeless nature of the Good to bolster his case. The Logos emerges as an interpretive tool and mediator: a divine reason or word through which God interacts with the world without being contaminated by change. The Logos allows for providential governance and revelation while preserving the transcendence and immutability of the divine source. Philo's deployment of forms and intelligible principles helps him map a hierarchical cosmos in which God remains immutable at its summit.

Practical and ethical implications
Immutability has moral consequences in Philo's thought. Because God is the perfect model of wisdom and justice, human beings attain virtue through imitation of the divine order, aligning soul and reason with immutable principles. Prayer, law, and moral striving are thus reoriented: they are not attempts to alter God but to transform the human soul so it harmonizes with the eternal rationality that governs creation. Philo therefore links metaphysical doctrine and ethical discipline, presenting immutability as a basis for stable moral life under providence.

Legacy and significance
Philo's insistence on divine immutability helped shape later Jewish and Christian theological debates about God's nature, providence, and the problem of evil. His synthesis of Scripture and Hellenistic philosophy offered a model for reading sacred texts philosophically while resisting crude literalism. By preserving the transcendence and simplicity of God alongside a robust account of divine action mediated through the Logos, Philo provides a resource for thinking about how an unchanging divine principle can meaningfully relate to a changing world.