Because that (dioti). As in verse Romans 19 . Knowing God (gnonte ton qeon). Second aorist active participle of ginwskw, to know by personal experience. Definite statement that originally men had some knowledge of God. No people, however degraded, have yet been found without some yearning after a god, a seeking to find the true God and get back to him as Paul said in Athens ( Acts 17:27 ). Glorified not as God (ouc w qeon edoxasan). They knew more than they did. This is the reason for the condemnation of the heathen ( Acts 2:12-16 ), the failure to do what they know. Their senseless heart (h asuneto autwn kardia). Kardia is the most comprehensive term for all our faculties whether feeling ( Romans 9:2 ), will ( 1 Corinthians 4:5 ), intellect ( Romans 10:6 ). It may be the home of the Holy Spirit ( Romans 5:5 ) or of evil desires ( Romans 1:24 ). See Mark 7:21 for list of vices that come "out of the heart." Asuneto is a verbal adjective from sunihmi, to put together, and a privative, unintelligent, not able to put together the manifest evidence about God (verse Mark 20 ). So darkness settled down on their hearts (eskotisqh, first aorist ingressive passive of skotizw, to darken).