Lexicon

G4893 - syneidesis

Strong's: G4893 · BLB lookup Pronunciation: soon-i'-day-sis Part of speech: feminine noun Root: sun- (with / together) + eidēsis (knowing), literally "co-knowledge" / "knowledge-with-oneself" NT occurrences: 30

Semantic range (Thayer / BDAG)

The conscience, the inner moral faculty by which one knows oneself morally
Moral consciousness / awareness, knowing-with-oneself about right and wrong
Self-judgment / inner witness, the faculty that accuses or excuses

The Latin conscientia (translating syneidēsis) preserves the same etymology, con- + scire = "knowing-with."

Theological force

Conscience is the internal moral faculty by which the person stands in self-judgment. The NT pattern:

Universal conscience (anthropological foundation)

Romans 2.14-15, Gentiles, "not having the Law… show the work of the Law written in their hearts, syneidēseōs bearing witness, their thoughts alternately accusing or else defending them"

This is the foundational text. Universal moral knowledge is grounded in the syneidēsis, built into every human as part of the imago Dei.

Spectrum of conscience-states

Scripture distinguishes various states of conscience:

Good conscience, Acts 23:1; 1 Tim 1:5, 19; 3:9; 2 Tim 1:3; Heb 13:18; 1 Pet 3:16, 21
Clean conscience, 1 Tim 3:9; 2 Tim 1:3
Pure conscience, 2 Tim 1:3
Weak conscience, 1 Cor 8:7-12 (the over-scrupulous)
Defiled conscience, 1 Cor 8:7; Titus 1:15
Seared conscience, 1 Tim 4:2 (kekautēriasmenōn, "branded as with a hot iron"; the conscience that has lost sensitivity through persistent rebellion)
Evil conscience, Heb 10:22

The conscience is universal but educable, it can be informed, refined, hardened, or seared. It is a moral compass but not infallible, it requires Scripture-formation to be reliable.

Christ purifies the conscience

Hebrews 9:14, Christ's blood "cleanse[s] your syneidēsin from dead works to serve the living God"
Hebrews 10:22, drawing near with hearts sprinkled clean from an evil syneidēseōs
1 Peter 3:21, baptism "an appeal to God for a good syneidēseōs"

The atonement purifies the conscience, addressing not just legal guilt but inner moral consciousness.

Pauline conscience-ethics

Paul develops conscience extensively in 1 Corinthians 8-10 (the food-offered-to-idols question):

The strong's conscience permits eating; the weak's conscience condemns it
Each must act according to their own conscience
The strong must defer to the weak, never violate the brother's conscience

The pattern: conscience is binding. Even an erring conscience binds, to act against one's conscience is to sin (Rom 14:23, "whatever is not from faith is sin").

Conscience and natural law

The conscience grounds the natural law tradition (Aquinas's lex naturalis; Reformed scholastic engagement). Romans 2:14-15 + the imago Dei (Gen 1:27) → universal moral knowledge → universal moral accountability → universal need of the gospel.

Modern engagement: C. S. Lewis (The Abolition of Man, 1943), the cross-cultural "Tao"; Edward Feser (The Last Superstition, 2008), natural-law tradition; Robert George (Conscience and Its Enemies, 2013).

Notable verses

Romans 2.14-15, universal conscience
Romans 9:1, Paul's conscience confirming truthfulness in the Holy Spirit
Romans 13:5, "be in subjection… for syneidēsin's sake"
1 Corinthians 8:7-12; 10:25-29, weak / strong conscience and food
2 Corinthians 1:12, Paul's "good syneidēsis" as testimony
2 Corinthians 4:2, "by the manifestation of the truth commending ourselves to every syneidēsei of men"
1 Timothy 1:5, 19, good syneidēsis paired with sincere faith
1 Timothy 4:2, seared syneidēsis
Hebrews 9:14; 10:22, syneidēsis purified by Christ

Patristic / scholarly note

The conscience-language is foundational to Christian moral theology:

Augustine, extensive engagement (Confessions; On Christian Doctrine)
Aquinas (Summa I, q. 79, a. 12-13), synderesis (the underlying habit / capacity) vs conscientia (its application)
Reformation: Luther (The Freedom of a Christian); Calvin (Institutes III.19; IV.10)
Modern: Robert George (Conscience and Its Enemies, 2013); J. Budziszewski (What We Can't Not Know, 2003); J. Daryl Charles (Retrieving the Natural Law, 2008)

Notes

Lexical workspace for syneidēsis.