{Because that} (dioti). As in verse  19 . {Knowing God}
(gnontes ton theon). Second aorist active participle of
gin(9373)k(935c), 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 ( Ac 17:27 ). {Glorified not as God} (ouch h(9373) theon
edoxasan). They knew more than they did. This is the reason for
the condemnation of the heathen ( 2:12-16 ), the failure to do
what they know. {Their senseless heart} (h(8820)asunetos aut(936e)
kardia). Kardia is the most comprehensive term for all our
faculties whether feeling ( Ro 9:2 ), will ( 1Co 4:5 ), intellect
( Ro 10:6 ). It may be the home of the Holy Spirit ( Ro 5:5 ) or
of evil desires ( 1:24 ). See  Mr 7:21f.  for list of vices that
come "out of the heart." Asunetos is a verbal adjective from
suni(886d)i, to put together, and a privative, unintelligent, not
able to put together the manifest evidence about God (verse
 20 ). So darkness settled down on their hearts (eskotisth(885c),
first aorist ingressive passive of skotiz(935c), to darken).