They know not, nor do they discern: The pronoun They refers to the idol makers, which is clear from verse 19. New American Bible understands this pronoun as pointing to “The idols,” but this is unlikely. In these two parallel clauses the prophet says idol makers are totally ignorant. They lack insight and understanding. Good News Translation expresses it bluntly with “Such people are too stupid to know what they are doing,” and so does Bible en français courant with “Those people have nothing in the head, they understand nothing.”

For he has shut their eyes, so that they cannot see: The Hebrew particle ki rendered for introduces the reason why the idol makers are ignorant. It is because they refuse to learn the truth. The pronoun he could refer to God or the idol makers. It probably refers to the idols makers, so there is a switch between plural and singular pronouns for them, which is not unusual in Hebrew poetry. Translators may use plural pronouns throughout this verse (so Good News Translation, Revised English Bible, New Jerusalem Bible, Bible en français courant). He has shut their eyes is an idiom for their refusal to learn the truth. The Hebrew verb rendered shut actually refers to covering something or smearing some substance over the top of something, so New Jewish Publication Society’s Tanakh renders he has shut their eyes as “Their eyes are besmeared,” and Bible en français courant says “They have their eyes glued.” Good News Translation uses an active verb, saying “They close their eyes.” So that they cannot see is the result of their refusal to learn the truth. It an idiom for their ignorance (compare 6.10; 32.3; 42.18-20; 43.8).

And their minds, so that they cannot understand is parallel to the previous two clauses The verb shut is implied here, so translators may repeat it if necessary. Minds is literally “hearts,” which is where thinking takes place in Old Testament thought. The Hebrew verb for understand is close in meaning to the one for discern.

For the translation of this verse consider the following examples:

• They do not know anything nor do they discern anything. The reason is they have [or, he has] smeared their eyes, so they cannot see anything. They have [or, He has] smeared their minds, so they cannot understand anything.

• They know nothing nor can they comprehend anything. Their eyes are blinded, so they cannot see anything; their minds are closed, so they cannot understand anything.

• Those people do not understand anything at all, because their eyes are shut so that they cannot see anything, and their minds are shut so that they cannot understand anything.

Quoted with permission from Ogden, Graham S. and Sterk, Jan. A Handbook on Isaiah. (UBS Helps for Translators). New York: UBS, 2011. For this and other handbooks for translators see here .