The Greek verb apalgeo means to become callous, to cease to feel pain, to be past feeling. Appearing only once in the New Testament (Ephesians 4:19), it describes the moral and spiritual hardening that results from persistent rejection of God's truth — a state where the conscience no longer registers the pain of sin.
Apalgeo is formed from apo (away from) + algeo (to feel pain). The word describes the final stage of spiritual desensitization. Paul writes in Ephesians 4:18–19: 'They are darkened in their understanding and separated from the life of God because of the ignorance that is in them due to the hardening of their hearts. Having lost all sensitivity, they have given themselves over to sensuality so as to indulge in every kind of impurity.' The progression is devastating: first ignorance, then hardness of heart, then the loss of all feeling — apalgeo — then unrestricted sensual indulgence. The word describes a moral callus: skin that has been repeatedly injured develops hardened tissue that no longer feels. Similarly, a conscience that is repeatedly ignored and overridden eventually stops functioning as a moral warning system. This is the NT's most clinical description of reprobation in progress, and it serves as an urgent call to keep the conscience tender through attentiveness to God's Word.