Exploring the Meaning of Kardiognostes in Greek

Kardiognostes means “heart-knower.” It appears twice in Acts, describing God (and addressed as Lord) as the one who knows what is in the hearts of people in decisive moments of communal discernment.

Root and Related Words

Kardiognostes is built from two elements reflected in related Greek words: kardia (καρδία), “heart,” and ginosko (γινώσκω), “to know.” Together they form a title-like expression that attributes knowledge of the human heart to God.

Occurrences

“They prayed and said, “You, Lord, who know the hearts of all men, show which one of these two you have chosen” (Acts 1:24)

In Acts 1:24 the word functions as a direct address within a prayer: “You, Lord, who know the hearts of all men.” The speakers are not merely saying that the Lord has information; they appeal to him specifically under the description that he is the one who knows hearts. That description grounds the request that follows—“show which one of these two you have chosen”—by locating the decision with the one competent to judge what is inward and personal. The scene, as presented in the verse, is a choice between “these two,” and the prayer frames the selection as something the Lord can reveal precisely because he “know[s] the hearts of all men.” The word thus supports the logic of the petition: when external considerations alone cannot settle a matter, the community appeals to the divine knower of hearts to disclose the chosen person.

The wording also stretches the scope beyond the immediate candidates by adding “of all men.” In this prayer, heart-knowledge is not limited to a particular individual or situation; it is presented as a comprehensive divine capacity. Within the verse’s short compass, the heart becomes the decisive domain for the selection, and the Lord’s heart-knowing becomes the warrant for expecting a clear indication—“show”—in a moment where human perspective is implied to be insufficient.

“God, who knows the heart, testified about them, giving them the Holy Spirit, just like he did to us.” (Acts 15:8)

In Acts 15:8 the word is used as a descriptive clause: “God, who knows the heart, testified about them.” Here heart-knowing is tied to God’s public confirmation—he “testified”—and that testimony takes a concrete form in the sentence itself: “giving them the Holy Spirit.” The verse presents God’s knowledge of the heart as relevant to his evaluation of “them,” and it portrays his verdict as enacted rather than merely announced. The giving of the Spirit is the visible action that the speaker points to as divine testimony.

The phrase “who knows the heart” also strengthens the comparison that closes the verse: “just like he did to us.” The heart-knower is portrayed as consistent in his dealings across groups (“them” and “us”), and his testimony is grounded in his ability to know the heart. Within the line of thought encapsulated by this single verse, heart-knowledge explains why God’s action counts as testimony: the one who knows the heart is qualified to confirm people, and his confirmation is expressed through what he gives. The word therefore connects inner knowledge (heart) with outward divine action (testimony by giving), joining the invisible and the observable within the argument of the verse.

Sense and Usage

Across these two occurrences, kardiognostes operates as a divine descriptor invoked at points where the inner life of persons is central to a communal decision or assessment. In Acts 1:24, heart-knowing is appealed to so that the Lord might “show” which candidate he has chosen. The verse links heart-knowledge with selection: the Lord’s choice is assumed to be informed by what is in the heart, and the community seeks disclosure of that choice. In Acts 15:8, heart-knowing is linked with testimony: God’s action of “giving them the Holy Spirit” functions as his witness about them, and the description “who knows the heart” underwrites the credibility of that testimony. In both scenes, heart-knowledge supports confidence in divine judgment—whether the judgment is sought as guidance (“show which one”) or cited as evidence (“testified about them”).

The word’s force also comes from how it speaks about “heart” as the relevant arena of knowledge. The verses do not specify what is in the heart, but they treat the heart as the place that matters for the questions at hand: who is chosen, and how God has borne witness about a group. By using a term that combines heart and knowing, the passages compress into a single descriptor the idea that God’s understanding reaches beyond what people can directly see. That compression matters rhetorically: it lets the speaker move quickly from describing God to drawing a conclusion—either a request for guidance or a claim about God’s validating action—without pausing to argue that God is capable of such insight. The descriptor itself carries the weight.

The usage in Acts also shows that heart-knowing is not presented as bare omniscience in the abstract but as knowledge with implications for action. In Acts 1:24, the community’s prayer assumes that the Lord can communicate his choice (“show”) in line with his heart-knowing. In Acts 15:8, heart-knowing is attached to God’s concrete deed of giving, which is treated as testimony. In both, heart-knowledge is the basis for an outcome that affects the community: appointing one of two, and recognizing God’s work “just like he did to us.” The title thus functions in Acts as a bridge between divine insight and communal clarity.

Imagery

Even in these brief sentences, the imagery suggested by kardiognostes is vivid: the heart is pictured as something truly knowable to God, and that divine knowing stands behind decisions and confirmations that become visible in the community. Acts 1:24 presents a scene of prayer seeking a revealed choice from the one who “know[s] the hearts of all men,” and Acts 15:8 presents God’s heart-knowing as the credential for his testimony expressed in giving the Holy Spirit “just like he did to us.”

Sources: Lexical data from Strong’s Exhaustive Concordance and the Translators Brief Lexicon of Extended Strongs for Greek (STEPBible, CC BY). Occurrence data from the Translators Amalgamated Greek New Testament (STEPBible, CC BY). Scripture quotations from the World English Bible (public domain).