To know madness and folly - A knowledge of folly would help him to discern wisdom, and to exercise that chief function of practical wisdom - to avoid folly.
Other Barnes' Notes entries containing Ecclesiastes 1:17:
DISCLAIMER: Church of the Great God (CGG) provides these resources to aid the individual in studying the Bible. However, it is up to the individual to "prove all things, and hold fast to that which is good" (I Thessalonians 5:21). The content of these resources does not necessarily reflect the views of CGG. They are provided for information purposes only.