Strange enough: it is a confessed darkness. There is a sort of common light that tells a man that impenitence is darkness. And yet it does not teach him better. Like mere physical light at times, some chemical ray is absent. The darkness that remains is a darkness that may be felt. It constitutes our eternal chains (2 Pet. ii. 4); it binds a man on the car of ruin. And like a Christian, who, in his partial light, may fail to know what is blessing him, so the sinner in his absolute darkness, takes industry for virtue, and family love for wholesome righteousness; and does not know the incidents of life that are stumbling blocks to eternal ruin.--_Miller._ Sinners are in such darkness that they are insensible to the objects that are leading them to ruin, thus they stumble--1. At the great deceiver. 2. At one another. 3. At Divine Providence. 4. At their common employments. 5. At the nature and tendency of their religious performances. 6. At the preaching they hear. 7. At the blindness of their hearts.--_Emmons, from Lange's Commentary._ _MAIN HOMILETICS OF THE PARAGRAPH.--Verses_ 20-27. THE PATH OF SAFETY. _For Homiletics on Verses_ 20-22, _see chap._ ii. 1-5, _etc._ Verses 23-27. +I. A man's most precious and real possession.+ "Thy heart." The heart here, and in other parts of Holy Scripture, is that part of a man for which the Bible exists, that in man to which the revelation of God appeals, that which places a great gulf between him and all other creatures in the world, that which links him to the angels of God, that which entails upon him responsibilities and endows him with capabilities which will last throughout all the ages to come. It is that spiritual nature which our Lord calls a man's "own soul" (Matt. xvi. 26), which Paul speaks of as the "inner man" (Ephes. iii. 16). +II. The need of "keeping," or "guarding" the heart.+ There are elements of evil as well as good in it. In any kingdom where there are bad subjects as well as good, there must be a watch kept over those out of whom submission to law is not to be got voluntarily. They must be guarded lest they get the upper hand and overpower and tyrannise over the peace-loving obedient citizens. In every human body there is some organ which is more prone to disease than others. While some are strong and vigorous, others are more or less delicate; therefore a man needs to exercise care over his body. So in the heart of the child of wisdom there is an evil element as well as a good one. "I see another law in my members," says Paul, "warring against the law of my mind" (Rom. vii. 23). Every godly man has a tendency to moral weakness, some opening in his spiritual armour, some weak part in his moral constitution. Therefore it behoves him to keep guard over, to watch vigilantly, the lawless, rebellious, or diseased elements within him, lest sin have dominion, if only for a time, where grace ought to rule.