Lexicon

G4100 - pisteuo

Strong's: G4100 · BLB lookup Pronunciation: pist-yoo'-o Part of speech: verb Root: from G4102 - pistis (πίστις, "faith / trust") NT occurrences: ~244

Semantic range (Thayer / BDAG)

To think to be true, to be persuaded of, to credit, intellectual assent; agreeing that a proposition is true.
To trust, to have confidence in, to entrust oneself to, relational; staking oneself on something or someone.
In Johannine usage especially: to commit oneself to Christ in saving faith, the comprehensive sense involving knowledge, assent, and trust (notitia, assensus, fiducia in Reformation theology).

Theological force

The verb's grammatical construction in NT Greek does theological work:

πιστεύω + dative, to believe a person, accept their testimony as true (pisteuō tinī).
πιστεύω + ὅτι (hoti), to believe that something is the case (propositional belief).
πιστεύω + εἰς (eis) + accusative, to believe into, to commit oneself to, place trust in, transfer allegiance to. This is John's signature construction for saving faith. (John 3.16 πᾶς ὁ πιστεύων εἰς αὐτόν; John 3:18; 1 John 5:13.)

The shift from believing that to believing into is the difference between intellectual assent and personal commitment. James 2:19 ("the demons also believe, and shudder") shows that pisteuō in the propositional sense alone does not save, even demons grasp the truth of monotheism. Saving faith (pisteuō eis) is committed trust, not bare assent.

This construction underwrites the Reformation doctrine of sola fide, salvation through faith alone, where "faith" is not mere belief-that but trust-in. The Roman Catholic and Reformed traditions agree on the threefold structure of saving faith: knowledge (notitia), assent (assensus), and trust (fiducia); the difference is over the role of faith (instrument of justification vs initiating sacrament).

Notable verses

Saving faith, pisteuō eis

John 3.16, "whoever believes (pisteuōn eis) in Him shall not perish but have eternal life"
John 3:18, "He who believes in Him is not judged"
John 3:36, "He who believes in the Son has eternal life"
John 6:29, "this is the work of God, that you believe in Him whom He has sent"
John 11:25-26, "everyone who lives and believes in Me will never die"
John 14:1, "believe in God, believe also in Me"
Acts 16:31, "believe in the Lord Jesus, and you will be saved"
Romans 10:9-10, "if you believe in your heart that God raised Him from the dead"

Propositional belief, pisteuō hoti

John 11:27, "I have believed that You are the Christ, the Son of God"
John 16:30, "by this we believe that You came from God"
John 17:21, "that the world may believe that You sent Me"
Hebrews 11:6, "without faith it is impossible to please Him; for he who comes to God must believe that He is, and that He is a rewarder"

Believing testimony / a person, pisteuō + dative

John 5:46, "if you believed Moses, you would believe Me"
John 5:24, "he who… believes Him who sent Me"
Acts 8:12, "believed Philip preaching the good news"
1 John 4:1, "do not believe every spirit"

Faith as the work / opposite of unbelief

John 6:29, "the work of God: believe in Him whom He has sent"
Mark 9:24, "I do believe; help my unbelief"
John 20:27, "do not be unbelieving, but believing"
John 20:29, "blessed are they who did not see, and yet believed"

Demonic assent, non-saving "belief"

James 2:19, "the demons also believe, and shudder", propositional belief is not saving faith
James 2:14-26, "what use is it… if someone says he has faith but he has no works?"

Connection to OT, aman / faith of Abraham

Genesis 15:6: "Abraham believed (LXX: episteusen) the LORD, and He reckoned it to him as righteousness." This verse is foundational for Pauline theology of justification by faith (Romans 4; Galatians 3). The Hebrew root aman (H539), root of "amen", combines reliability and trust. The LXX renders it with pisteuō, locking in the linguistic bridge from Hebrew faith to Greek-NT faith.

Patristic / scholarly note

Augustine (De Trinitate 13.2; Tractates on John) develops the threefold structure of faith: credere Deo (believe God, assent to His testimony), credere Deum (believe that God exists, propositional), credere in Deum (believe into God, wholehearted trust). Only the third is saving. Aquinas (ST II-II, q.2, a.2) systematizes this into fides informis (mere intellectual assent) vs fides formata (faith formed by love, the saving kind).

The Reformation pressed fiducia (trust) as the heart of saving faith against medieval scholastic emphasis on assensus. Luther's Bondage of the Will (1525) and Calvin's Institutes III.2 treat pisteuō as the receptive instrument of justification, the empty hand that grasps Christ's righteousness.

Verses in this codex

See Obsidian's backlinks pane for every verse page linking here. Top-cited references using pisteuō: John 3.16, Romans 10.13 (closely related construction), John 1.14 (paired with monogenēs).