### Core Meaning & Semantic Range
The Greek word αἴτιος (G159), transliterated as *aítios*, is derived from the same root as αἰτέω (G154), meaning "to ask, beg, or demand." This etymological connection points to a core meaning related to responsibility or the source of something. Primarily, αἴτιος functions as an adjective meaning "causative," "responsible for," or "guilty of." When used concretely as a noun, it signifies "a causer," "an author," or "an originator." The semantic range thus encompasses not only the act of causing but also the state of being accountable or the very origin point of an event or condition. It carries a strong implication of being the underlying reason or force behind a particular outcome, often with an ethical or legal dimension in classical Greek usage.
### Biblical Occurrences & Contextual Analysis
The term αἴτιος (G159) appears only once in the New Testament, but this singular occurrence is profoundly significant.
* **[[Hebrews 5:9]]**: "And having been made perfect, He became the author of eternal salvation to all who obey Him."
* In this pivotal verse, αἴτιος is translated as "author." The context is a theological exposition on the high priesthood of Jesus Christ. The preceding verses discuss Christ's suffering and obedience, through which He was "made perfect" (τελειωθείς). This perfection is not a moral improvement from a flawed state, but rather the completion of His redemptive work and His full qualification for His high priestly office.
* By stating that Christ "became the αἴτιος of eternal salvation," the author of Hebrews asserts that Jesus is not merely an initiator or a guide, but the very *cause*, *source*, and *responsible agent* of salvation. His perfected obedience and atoning work are the *means* by which eternal salvation is secured and made available. This highlights His unique and indispensable role in the economy of redemption. The use of αἴτιος emphasizes the causative power and efficacy of His finished work.
### Related Words & Concepts
* αἰτέω (G154): The root verb, meaning "to ask, demand." While αἰτέος (G159) describes the one who *causes*, αἰτέω describes the act of making a request. The connection underscores the idea of a reason or origin behind an action or state.
* ἀρχηγός (G747): Often translated "author," "leader," "founder," or "pioneer." This term is also used in Hebrews to describe Christ (e.g., "author of salvation" in [[Hebrews 2:10]]). While both αἴτιος and ἀρχηγός can denote an "author," ἀρχηγός often emphasizes being the *first* or the *leader* who blazes a trail, whereas αἴτιος (G159) more directly emphasizes being the *cause* or the *source*, the one responsible for bringing something into existence or effect. In [[Hebrews 5:9]], αἴτιος might place more emphasis on the causative efficacy of Christ's perfect obedience rather than solely His pioneering role.
* πρωτότοκος (G4416): "Firstborn." While implying preeminence and origin, it typically refers to status or position rather than direct causation.
* κύριος (G2962): "Lord." This title implies ultimate authority and sovereignty, which naturally extends to being the ultimate cause and source of all things within one's dominion.
### Theological Significance
The singular application of αἴτιος (G159) to Jesus Christ in [[Hebrews 5:9]] carries profound theological weight.
* **Christ's Sole Causality in Salvation:** It definitively establishes Jesus as the unique and ultimate *cause* of eternal salvation. He is not merely a facilitator or a prophet, but the very divine agent through whom salvation is wrought and made available. This underscores the exclusivity and sufficiency of Christ's work for redemption.
* **Divine Agency and Responsibility:** The word highlights God's active and decisive agency in salvation, specifically through the person and work of Christ. It speaks to the divine initiative and responsibility for securing humanity's eternal well-being.
* **Perfection as the Ground of Salvation:** The phrase "having been made perfect, He became the αἴτιος" directly links Christ's perfected state—achieved through His obedience and suffering—to His capacity to be the author of salvation. His completed work and qualification as High Priest are the necessary and sufficient conditions for the salvation He provides. This perfection is the causal basis.
* **Eternal Scope:** The phrase "eternal salvation" emphasizes the enduring and ultimate nature of the salvation Christ causes. It is not temporary or partial, but a complete and everlasting deliverance.
### Summary
The Greek word αἴτιος (G159), meaning "causative" or "the causer," holds a pivotal place in New Testament theology despite its single occurrence. In [[Hebrews 5:9]], it describes Jesus Christ as the "author of eternal salvation." This designation signifies that Christ is not merely an initiator or a leader, but the fundamental *source*, *originator*, and *responsible agent* for salvation. His perfection, achieved through obedient suffering, is presented as the direct cause and enabling power behind the eternal salvation offered to all who obey Him. Thus, αἴτιος underscores Christ's unique and indispensable divine agency in the work of redemption, establishing Him as the ultimate ground and provider of eternal life, a truth foundational to Christian understanding of salvation.