Why did Paul constantly put himself down as nothing?
Paul constantly put himself down as nothing because he realized that God cannot use somebody unless they are nothing. Even though Paul was highly educated and moved in the upper echelons of Judaism, he understood that God uses those who do not rely on human power, pomp, or wisdom.
Les explains that Paul was really an exception, because Paul was highly educated and no doubt had a lot of polish, since he moved in the upper echelons of Judaism. Yet this is why he constantly puts himself down as nothing: he realizes that God cannot use somebody unless they are nothing. The broader context shows that God does not usually call the wise, mighty, or noble, nor does He usually go into the ivy-covered halls of universities for His servants. In the Old Testament, God used common, ordinary members of the Jewish nation like Amos, Gideon, and Ezekiel, because that is what God saw fit to use. The prime example is Moses: after his first forty years in Pharaoh's palace, as the second top man in Egypt, Moses thought he could take the children of Israel out of slavery by his own power, pomp, circumstance, wisdom, and leadership.