How should you determine whether God is dealing with Israel nationally or personally?
Determine it by examining each Scripture passage's context: ask whether God is addressing Israel as a nation under the covenants or addressing an individual Israelite. Most often He deals with them nationally, because the covenants pertain to the nation, though an individual Jew can still be saved even while the nation remains spiritually blind.
Les teaches that Scripture shows God dealing with Israel on two levels, national and personal. Therefore, you must always look at the passage and ask whether He is dealing with the nation as a nation under the covenants, or with an individual. Les explains that most of the time God deals with them on the national level, because that is where the covenants come in. Yet an individual of Israel can still even today be saved, though nationally the Jew is blind. That blindness does not mean an individual Jew cannot come and enjoy salvation. The lost coin is left as the condition of the nation of Israel, that which was God's by covenant promises, while the lost one is the one He brought to Himself, just like the little lost sheep.